There a lot of counterfeit radio microphones on e-bay currently.
How can you spot them?
Well the problem is, you can't. Not from the pictures anyway. Not from the descriptions either. Largely because the pictures and blurb are simply cut and pasted from the websites of the genuine article anyway. That in itself is a total con by the way, and they haven't even got your money yet. BUT: there is one very easy rule of thumb that you can use as a guide, and it is this:
IF IT LOOKS TOO GOOD TO BE TRUE, IT IS TOO GOOD TO BE TRUE!!!
Please use your common sense. If the best price you can find on a Google search is £400, but someone on e-bay is selling it brand new for £199, they are are trying to con you. You CANNOT buy a genuine breand new radio mic on e-bay for half of what it costs in a bona fide shop. Of course you can't!! So do not buy these things from these people. You are NOT buying the item they are pretending to be selling. You are being stitched up with some sub-standard piece of rubbish that will not perform like you want and expect it to. And it will break. And when it breaks there is nowhere you can take it to get it repaired. Your vendor won't do it, and neither will the brand manufacturer. (Because they didn't actually manufacture this in the 1st place!)
If in doubt, check with the genuine manufacturers - Sennheiser, Shure, AKG, Audio Technica, etc. They will be delighted to advise you properly.
"You get what you pay for" - with counterfeit radio mics, that age old addage is as true as it ever was!