Has anyone here had it done??

We've recorded a bunch of songs ourselves and they're pretty much done, though they're extremely dynamic. Now I like dynamic records, but after listening to the songs in my car they seem quite....Spiky

They sound good, I recorded them in Logic and we used pretty decent equipment, but I know not to mess with mastering unless you have the know how and stellar monitors/plug-ins.

So if you've had it done, where did you get it done? Do you just send it off to a mastering studio and hey-presto?

Also cost, if it costs too much then we may just leave it until we release something bigger. Would it kill my wallet?