If you live in a big city, that might not be feasible. But do try to visit more than just a few schools. Also, you must visit a school more than once to form a valid opinion. Cost is neither the most nor the least important factor in your decision. You must weigh it according to your own priorities.
Prices vary widely.
Some schools give you a price break if you pay lump sum for several months. Some schools require you to sign a long-term contract to join. To discuss all of the different ways to pay and the associated legalities is beyond the scope of this humble document. Many schools charge an additional fee for each belt test. The fee may be different depending on rank.