How much do you pay to get tires mounted?

Doing it at home.   Yes it is worth it.

I pay $Free.99, but I have an unfair advantage, because I'm a mechanic and can use my shop's tire machine.

It depends on where I buy my tires.  If I get them through the local Discount Tire then they're mounted for free.  If I buy used or from tire rack then I pay $20.00/tire.

I've thought about getting my own equipment but so far I haven't thought it was worth it.  I don't have a lot of shop space, even at $20/tire you can mount and ballance a lot of tires before you cover the cost of the equipment and I really don't enjoy mounting and balancing tires.

DIY, using work's equipment. The downside is the stuff is at a second location that I almost never work at and is out in the middle of nowhere. So my cost is ~$10 of fuel and 1.5hrs of my time to drive there and back. Still generally worth it but it's annoying; I will occasionally pay to get a set mounted locally if I'm in a hurry and don't have a day to burn on it. If I had space at home and a better compressor I'd be at least seriously considering buying my own equipment.

Doing it at home. Definitely worth it. 

$60 for 4 and I give the guy a $20 tip, so $80 total. 

My most recent order from Tire Rack cost me $120 for mounting. That didn't include disposal, I kept the old tires. 

I can't say what is reasonable, small businesses have to charge enough to stay in business and provide a reasonable income for the employees and the owner.
 

Still, that's a lot to add to a set of tires. Two years ago I paid $80 at the same place. 

A shop I use on occasion for oil changes on the Suburban and repairs that I can't do charges $25 a tire.  A small tire shop in the county charges $15 per.

A shop I use charges $20 per tire, not including disposal.  That adds an extra $7 so i just collect them until i make a dump run. 

I was paying between $20-25 per tire, a used tire machine quickly paid for itself.