Charged, yeah, it can be tough to decide which one is which, but generally all these engines are the same. I got mine from powerking, on EBay with a winning bid of $125. It's an 80cc and came with free shipping and haven't had any serious issues with it yet.
But really what you need to know is that it's not the price but the customer service that comes with it. Some of the folks, here on this site, that sell these engines have warrantees on them and are fairly priced. When it comes to breakdowns and warrantees, will Boygofast honor it? Maybe, but doubtfull.
Don't feed the bears....