I used to be a hardware reviewer for a small site in the Benelux. Unless the item was something that you "spent" while testing it (kinda stupid to rebottle liquid cooling fluid for instance), the items tested were either to be returned or to be bought at cost (or slightly above production cost, but definately below market value). Sometimes there were no provisions to let you keep it, even at a price. Big things (cases, motherboards, gfx cards, RAM, CPUs,...) were only very very rarely free. Happened maybe once or twice over a span of 10 years that I can remember, but never to an item that I was reviewing. Hardware companies are more likely to let you just keep it if you're a large review site, but that also makes sense since you might want to reuse it in another comparative test in the future. Yet these same items are likely to disappear into private possession, obviously. Is it a pay off? I don't know, because if done right it's hard to say if someone is genuinely impressed with a product because it's good or just because his review was "bought".