I am not talking about the TTD priests alone. I am talking about priests in all the temples.
But anyway, I am sure the priests in most of the temples (to my knowledge, that includes Tirupati too, and there was an article recently in a newspaper) are not well paid.
TTD may be using funds for religious activities.
The same can not be said for all other temples. Next time, when you visit any temple, look for a board which says, "Drop your offerings in hundi only". Also, look out for government executives (not in very small temples, but major temples), who keep watching where the devotees are dropping the offerings, and when they notice that the devotees are directly giving to thr priest, they keep a watchful eye to ensure that the priest drops the offerings back into the hundi.