While this is all fun & games hobby for many of us, for a retailer, this is how they MAKE A LIVING. They aren’t trying to make sales just for the sport of it. And every time they open a box, the next customer is going to expect and "open-box" discount of 5-10%. So really, the dealer is potentially losing money on every box he opens to do a demo. Even worse if that unit comes back with fingerprints, or gosh forbid, the tiniest of a scratch! Do you charge for that, or give the next buyer a discount??
My first encounter with a high-end dealer in 1984, I was in college, and they let me home demo an NAD 3020 amp. Well.... we all know what happened next, right? I was properly blown away, and bitten for life by the high-end bug. But their 3020 was already a showroom unit, and had probably been demoed in many homes. I was not asking the guy to loan me a ReVox integrated.
To finish the story.... I returned the 3020, and purchased a 3150, and soon after, a pair of Boston Acoustics A400 speakers. I’d never heard 30Hz until then!