I have bought a lot of scopes, lasers, sights etc from China...the main drawback I have found is that they don't adjust always in nice predictable clicks, they often have to be reset/re-zeroed after bouncing around in their cases etc...and like someone said, they are mostly designed for airsoft. But I use them mostly for recoiless .22 and they're fine. Some of the zoom scopes I have bought have a bit of distortion at the higher (10-16X) settings, but are fine under that. I have bought from Chinese sellers on Ebay.ca...one favourite is Red-Star## (some number, I forget). Takes a good 3-4 weeks to arrive. No customs hassle ever. Not under $100. Not yet, anyway, your "Conservative" Prime Minister says he's about to clamp down though. With free shipping, there is no need to combine your orders, or you may get dinged.
I would say they were not of the quality needed for much over 1-200 yards, IMO, or for wet/winter use. But for my needs, $60 bucks beats $600.
Other things, though, like bipods and rings and weaver rails etc etc...the ones I get from China are identicial, IMO, to the "branded" ones I have got for 5 times the price here at my LGS.
A (very) surprising source of "tactical" gear, including some with free shipping, is Amazon.ca!
Sorry retailers - I aways support y'all for guns 'n ammo, but I cannae afford 400% mark-up on bits of aluminum alloy and steel.