Nursys charges $30 for each state you apply to, not each state you hold a license in. If you are licensed in 20 states that all report to Nursys to apply for a license by endorsement to say Massachusetts (which requires verification of every license you've ever held), it costs you only $30.
Originally, Nursys would verify to any state for 30 days after you paid your $30. So you could apply to several states at once and just pay Nursys $30. But it wasn't as valuable as it sounds as many fewer states reported to Nursys. Now most do so the value proposition is actually better as few nurses apply for several licenses at once anyway.
There are still a lot states holding out from Nursys. My original state license was California, and I have to pay them $60 (for just that one state) every time I have to verify them for a new state license. Plus it must be done by snail mail and can take them over a month to return it to the state you are applying to.