How much will is cost to have a plumber snake my pipes?

I have a backup in one of my pipes. To begin with, the upstairs toilet was clogged (or so I thought), then the downstairs toilet clogged. Shortly thereafter, the shower in the downstairs bathroom backed up too. This has been going on for a while and every now and then when I run the shower for a while or occasionally when I run a load of laundry I'll hear the downstairs toilet burp and then all of a sudden that toilet will work again...for a while. Right now neither toilet is working and I need to know about how much this is going to cost to have fixed (in NJ).