600 is a pretty decent price for a full paint correction w/ opti coat. Pretty much any full correction is going to cost at least 500. Takes them forever since they have to work their way through so many levels of abrasives and polishes.
I've never had a full correction done since trying to keep a jet black daily driver swirl free is too much of an uphill battle for me. Every 6 months or so I just get a 2 stage polish to clean it up to where it looks smooth in the sunlight. You'd still see swirls and defects if you hit it with a shop light. Most dealerships, even higher end brands than bmw, are known to be pretty lazy when it comes to prep and car washes. Best to just leave that up to the pros or do it yourself.