I'm a brand new member, and I'd like to report my experiences with eBay flutes.
Here is my back ground with flutes:
I've been playing flute for about 30 years, on and off, mostly for my own pleasure. But I took lessons and played in Orchestra at university and played in (almost) semi-professional Latino-jazz band, among other things. I have played trumpet and clarinet, a little, too.
I own 2 professional flutes (No.1: YFL-61 Handmade Yamaha, open hole, inline G, sterling silver. No. 2: Rare Sakurai, also all hand made, silver, soldered tone hole, open hole, inline G).
They are highly reliable instrument and Sakurai still has all original pads, and I sent Yamaha to maintenance only once (for some repair and pads change). Other than that, I do all minor adjustment myself. but I don;t need to do much.
And I took this Yamaha to every where, around the world, even on the mountain bike trip on trails, going down hill at full speed with extreme vibration and shock and temperature range of -10 to +30. Yet this Yamaha is still playing very well without any problem. So, I know about good flute, a bit.
Recently, I got curious about cheap flutes at eBay, knowing very well that some of cheap flutes are actually lovely instruments, and I started to search and learn about them.
And I got some extra money due to lots of over-time work, I started to bid on cheap flutes (under $200).
I lost first couples of bids, but them learned how to win.
I bought 7 or 8 of them, so far, 3 of them are new or almost new, while others are used. Some of them were won by bidding, others were "buy it now" or by the best offer.
In general, all of them have been nice. I had no instrument that I had to throw away. But all used one required some adjustment, so far.
It means YOU SHOULD NOT BUY USED EBAY FLUTE UNLESS YOU CAN AT LEAST DO MINOR ADJUSTMENT and possibly some basic repair like changing cork.
All flutes were well packed and promptly shipped.
However, some of them tool time to arrive because I'm in Canada and you never know what happens at the border.
With a few of them, I had the surprise of paying relatively high custom broker charge plus Canadian Federal Sales tax (GST) costing nearly 30% of the price of the flute. So, Canadian buyers (and possibly other international buyers), be aware.
To make things worse, more expensive flutes are usually sent with UPS and insured, and that means UPS will be charging high custom clearing fee, while cheaper flutes are sent by USPS and usually there is nothing to pay (or sometime just sales tax = GST, which is just 5%).
Anyway, here is the list of what I got from Ebay, so far (more coming):
#1 Vintage Heimer $46: Closed hole el cheapo. According to some people, it's made in china.
The cork was dry (or too small) and it was totally loose, and moving around in the head joint....
I'll have to replace the cork, or put the all mighty plumbing white tape or something to make it fit. For now, I just fixed the head crown with scotch tape, and this made the flute playable.

Other than that, the mechanism for Bb with F key, and F# needed adjustment. And the head joint fit a bit loose to the main body.
After about 10 minutes of quick adjustment, flute became playable, and it wasn't bad, at all.
For the el cheapo Chinese flute, actually it's pretty good.
After about 5 minutes of testing, it sounded even better.
But it takes probably a bit of experience to make more or less good sound, and the tube feels heavy and doesn't vibrate as much as my handmade flutes.
It feels stiff and rigid a bit. I'll see if it changes with more testing, later.
#2 Vintage Armstrong 103 $115: Open hole inline G
This flute needed adjustment on Lowest C key, and F#.
Also, pads make sticky sound....
But this instrument surprised me with the sound. It's not exactly the same as my handmade flutes, but not so different.
When I think of the price, this one is $115 and I payed a bit more than $2000 for YFL-61 (about 30 years ago), and about $3000 for Sakurai (about 25 years ago), this Armstrong 103 is impressive.
I like it a lot.
I'm gonna buy the small bottle that supposed to eliminate sticky sounds of pads and see what happens.
#3 Vintage Artley 17-0 $43: Closed hole
I think this one needed just twisting one screw and put 2 springs back into position to make it payable.
Arrived in very well polished and cleaned. Lovely instrument and I can see it was taken care by the owner, very well.
Of all used flutes, this one is the prettiest flute, even though lip plate and B key and where we support flute has silver? plating nearly gone.
All other body is really shiny and perfect.
And it has rich velvet sound. Probably, previous owner played well, other than taking extremely good care of the instrument.
Best closed hole flute, so far.
#4 Vintage Armstrong 104 $39: Closed hole
This one is missing head crown .... I need to find replacement, somewhere...
And the pad on C trill is in bad shape, leaking a bit of air and making unwanted vibration. And it needed one or two key screws to be adjusted a bit.
Despite these problem, it's playable (after tightly cramping the leaky trill key with ... scotch tape, again

And even without the head crown, it makes amazing sound in the 2nd octave. But the lower register isn't so good. Maybe I need to practice a bit on this instrument to make better lower tones.
I think I like Armstrong flutes.
#5 Berklay hand engraved (new flute) $31: Closed hole
This is a brand new flute wrapped in plastic bag and paper !

I think this one in made in china, too. And this one also has slightly loose head joint...
But the sound is pretty different from the previous Chinese flute (Vintage Heimer). I think the tube is either thinner or made of different metal.
And the body color is brighter than all other silver (or silver plated) flutes.
So, it has slightly lighter brighter sound and less resistance.
I don;t know how reliable this instrument is, in long run, but hey, for $31 bucks, this is extremely good instrument.
I'm pretty glad that I won this at this low price.
Probably, I'm gonna give it to a kid in school band near by, or sell it cheap locally to someone who would like to play a bit, after testing it for a few months.
#6 (Fake) Yamaha 271S (directly from China) $119: Open hole, inline G.
As I'm a owner of REAL Ymaha instrument, I got curious about these fake Yamaha on Ebay.
So, I decided to buy one and test it.

It's not dirt cheap, but cheap enough to throw away and forget it.
After ordering, the guy became "unregistered" at Ebay. So, I was worried.
But it arrived, finally.
I don't know if it's gonna last or not, but as far as the sound is concerned, it's not bad at all.
I have played cheaper Yamaha before to by handmade model, and I remember how they were. Compared to them, this one sounds better.
Oh, it came with plastic hole plug. It felt terrible and I took it away in haste.

An just like two other Chinese flutes, the head joint is a bit loose!
I'm starting to wonder if ALL Chinese flutes have loose head joint ...
PS
So, these are the flutes I received, so far.
I'm still waiting for a few more to come, including famous (or infamous) Gemeinhardt M3 (supposedly new).
I'll report back when they arrive.
Up to now, my experience with cheap eBay flute is positive, even thought all used flutes needed some adjustment and repair.
It's not so difficult to make them playable (for testing and personal fun).
But it's a different story if they have to be playable for more normal/serious practice and band/orchestra playing.
In other words, someone who doesn't want to take the risk of adjusting and repairing by oneself or by repair person should avoid used cheap flute. (But I'm talking about really cheap one like I bought.)
There are used, but well serviced flute starting around $200 to $300, too.
And these are usually sold at more than double at the music store.
So, Ebay deal can be a good deal IF you know what you are doing., I guess.
As for the cheap and fake Chinese flutes, I tend to think they can be usable. But I'll report back after more testing and playing.
I've only played each instrument about 20 to 30 minutes.
I'll try to be a bit tough (as far as playing style is concerned) on them, and see what happens.