I think this is kinda contradictory...because on one hand, you want your own sound that you can push and people will hopefully come to you just for that sound that only you can do.
But on the other hand, the most beat sales I have had are from doing "imitation" style beats of other producers sounds. Rappers tend to hear a track on an album but can't afford the money to pay for the real producer to make a beat for them...so they hit up Google/music websites/Youtube and try to find the next best thing. Thats why a lot of these beats have a "INSERT NAME HERE style beat", because they want to catch the attention of the rappers looking for beats like that. It's good marketing.
The best sales I have achieved were back when Scott Storch was on top and I managed to get his sound down fair well...and whenever he produced a beat for 50 Cent or other artists, I would soak up sales based off of producing similar beats.
It's just marketing, really. Yes, you sell yourself out a bit and should really be finding your own sound, but...we've all gotta eat.