There is another thread that discusses pros/cons/likes/dislikes/etc of going MP/SP/SC. Each offers a different experience, simple as that...look up the other thread if ya want to delve into it deeper...
As for the math presented above, it's not cut and dry math as presented above. If you're Joe Casual SCer and go for 1-5 songs, then ya it is. Plus, when you get into larger numbers or dances...the good ones don't charge by song...but by the hour, like an SP. The standard in that regard is typically $300/hr, but if you get to know them (the good ones) they're less. I've done an hour for 2 bills at Pigs...
However, every dancer is different and you can pick them out easily enough without spending more than $20 on them.
Some like to converse and will take "timeouts" every couple of dances to just sit and talk...all while cuddling up and lightly caressing with you and not charging you just because a) they like you or enjoy your company, b) they want to "extend" their absence from the floor because of slow night or bad drunks that treat them lousy.
Bottomline, you get what you put into it. If you're not willing to spend the time to find the "good" ones and treat them well, etc...then you'll come away with the impression that many mistakenly seem to have about SCs...and like Tommy says...just because you "believe" there is no release involved doesn't mean thats true...