There is "good" grey market... and "bad" grey market.
"Grey market" simply refers to the way the gear is imported... not through official and manufacturer authorized channels. Grey market sellers leverage the fluctuations in currency exchange rates to eke out a little lower price, then bring the gear in via "the back door". In itself, this isn't necessarily a bad thing. B&H and Adorama practically invented the process and still do it a lot today. In most cases, the gear is exactly the same, you just don't have the same manufacturer's warranty with grey market. Most reputable grey market dealers like B&H and Adorama typically offer a "store warranty" instead... where you can return the gear to them for repair, if needed, during a certain period of time.
But there are also plenty of "scammers" using the grey market approach. They use bait and switch tactics, such as deleting necessary items that are normally included, then trying to sell them to you at greatly inflated prices.
You can check out practically anyone who sells online at
www.resellerratings.com If you look there, you'll find Focus Camera (aka digitalfotoclub.com) not getting very good reviews. Compare to B&H or Adorama, for example. Resellerratings.com is helpful, but I always take their 5-star reviews with a grain of salt. It is too easy for a dealer to have fake reviews posted, in hope of increasing their score.
It also doesn't always track that an online seller and a brick and mortar store of the same name will necessarily treat their customers the same. Sometimes online sales are done by a whole different, and much less trustworthy, division. It might even be a subsidiary or separately owned and operated. Plus it's generally harder to "put one over" on people in a brick and mortar store!
I noticed that you were specifically asking about buying from Focus Camera
through Amazon... That's a bit different than dealing direct. There are several sales models on Amazon... Amazon direct, fulfilled by Amazon and associate sellers within the Amazon community. If the first two, you don't have too much to worry about. They have a liberal return and refund policy. If the latter, an independent seller you deal with who happens to be on Amazon (which can be a store... or an individual selling a single, used item), Amazon tries to police them and won't tolerate a lot of complaints. So you have some recourse, if there is a problem and you want your money back.
I just did a quick search and found an example being sold by Focus Camera and Fulfilled by Amazon:
http://www.amazon.com/T5i-Digital-75-300mm-Telephoto-Accessory/dp/B00COR4Q2K/ref=sr_1_3?s=photo&ie=UTF8&qid=1440960644&sr=1-3&keywords=focus+camera&pebp=1440960652844&perid=1AC0R0K2N5Y4FJ8CWMW9In one respect I'd be okay buying that, since it's fulfilled by Amazon. But, looking closer at what's bundled in the offer, I see a lot of junk. Much of the "Deluxe Accessories" included trying to make me think it's a great deal are actually next to worthless (the 2.2X and .43X lenses, the filters, the no-name flash and more). Even the telephoto lens in this case is one of the manufacturer's cheapest (and one of their worst).
Caveat emptor!