You'll need to ask MSC about pricing of their products.
Do you need just a Nastran solver, or also a pre and post-procesor? MSC used to sell a product called Nastran4Windows that was FEMAP bundled with a basic version of MSC Nastran. It was fairly cheap, but MSC no longer sells that. They should be replacing it with a Patran/Nastran product, but I don't know the details.
You can get versions of both NE Nastran and NX Nastran bundled with FEMAP without spending too much. NX Nastran is almost identical to MSC (will give identical results in 99% of all cases) since they were exactly the same code up until MSC V2004. NE Nastran is different, but might also do the job for you depending on what your needs are.
As a general rule, the versions of the codes packaged with pre-post processors are cheaper than stand-alone versions. That's because they're designed to be used by a single user on a single computer rather than by a group over a network.