I really like this idea, in a flirting and humorous way. I would love to tell my SO he will get a blow job if he takes the trash out, washes my car or mows the lawn. It's likely that once we set the "price" I would not be able stay away from him long enough for him to finish his chore and he will get his reward anyway. In the same way, I feel cooking great meals and other household chores on my part should be rewarded as well, goes both ways. My SO will tell me what a good girl I have been and I deserve my "pay".
I know he will love reading this, enjoy baby.