I guess the deserve part threw me. I'm not sure deserve is the right word. I am inclined to say no not deserve. However, a previous poster brings up an interesting idea. If you the provider have to do less work verifying a client because he is white listed then that may warrant a discount. The argument by some providers on here that the white list is easier to get than a P411 Ok since P411 verifies the guys could come into play for you. If you believe the white list isn't worth as much as a P411 OK then the white list discount might not be something you would want to do.
Bottom line...it's up to you. If you give discounts do it for your reasons. I know some providers give discounts to TER VIP members. Giving discounts for being white listed makes as much sense as that and maybe more for the reason stated above.
I know if there were a provider I was interested in that offered discounts for being white listed I'd see her and likely often. It wouldn't have to be a large discount either.