Help buying arduino Mega clone board

Hi!!
I'm new in this wonderful world, and I'm looking for an arduino clone for the arduino Mega 2560 R3. Unfortunately, in this moment I can't afford to buy the original board, even though, in the future, I will. So I'd like to ask if there is any clone for this board that some people have tested before, and has fully compatibility with the original mega board (of course, I understand that the quality of the original can't be compared, but there are plenty of clones around the net and I'm not sure if all of them are worth the money)
Also, I don't feel really comfortable buying the board in ebay, cause there are so many fake boards, that you could end up with something completely useless, so it'd be really nice if you could also post the link where to buy it.
Thank you all in advance.

The cheapest non-eBay 2560 clone seems to be this one for $18.01 from China:

http://www.aliexpress.com/item/SINTRON-Arduino-MEGA-2560-R3-USB-cable-reference-PDF-files-for-starter/878813783.html?af=ppc&isdl=y&src=Google&albch=Google&albcp=Search_Search-ALL-PLA&albkw=None_US-Shopping-Search-Product-AliExpress_none_none&albag=home_none_Search-ALL-PLA_1013999999870&albmt=broad&albst=search-text&albom=OTHERS_None_20130807_Aliexpress&creative=31447451305&ptsid=1013999999870&gclid=CLroxq6fobwCFXNp7AodMSsAMw

It is seldom a matter of a particular vendor selling all bad boards. More often the failure rate for clone boards is higher than the failure rate for official boards. A basic eBay clone is likely to be just as good as a non-eBay clone. At least with eBay you get eBay's guarantee that you can get your money back.