Building a garage, cost $$$$

Hi Guys, I was thinking of getting a garage built in my backyard. Was thinking something along the lines of a 24x28 with a 10 foot height and a concrete pad. I received two quotes for this build, one was $15K and the other was $24K. Maybe I am behind the times here but I thought that was a lot! 12 years ago my father had one built 24x24, with a 8 foot height and concrete (he had to side it himself and roof it to save money) for $4500. Has anyone recently built a garage and is this the going rate??