I requested to do T&G's at a class B last week, but I was turned down. I went in the evening and approach said they were still too busy.
But I've known other people who have done T&G's at Class B's before at different times of the day and night. Why don't you call the tower or ask around and see what times they might let you do it?
Also, I doubt you will ever be asked to pay a landing fee. I've been in an ops tower at a class b before and when I asked them about fees for Cessnas and things they seemed like they didn't care about charging landing fees for GA planes. The money they earn off of a 737 is way more than what they can get off a 172 and plus it'll take some effort on their part to hunt you down and get your money.