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. Be sure to ask. When inquiring about costs, be sure to ask about costs that senior students pay, as well as what beginners pay. You will probably have to spend some bucks on an appropriate uniform or two. If you do this, the clothes you wear in the interim should be comfortable, secure, and modest.