well im gonna record a few covers to put on youtube but the studio i go to charges a lot for a not-so-good mixing.would it hurt much to not mix tracks? they put mics on every tom,the snare and hi hat and an over head
What exactly are they mixing...the individual mics to get a balanced overall kit sound? Because that shouldn't be an upcharge.

Or, are they mixing your drums with the track you're covering?

Either way, I expect you'll want to mix. The only way to know for sure is to get a copy from them of an unmixed recording and decide if it's worth it.