$100 for the front would be extremely cheap since they would have to drop the subframe to remove the brackets. In other words they won't and you'll still be out $100... (unless they're honest???)
Just buy a can of spray lube (lithium grease) and spray the front bushings. If they are stock rubber there should be plenty of gaps and cracks to let it in.
$80 for the rear is a major ripoff. It's 1 bolt in each bracket and can be done in just a few minutes all by yourself.
