#1
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
#2
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.