Your price seems reasonable. I just built a 24 by 28 with wooden framing. I poured the footer and foundation then built the structure. I plan on pouring the floor next year when I have the $$.
It cost me about $300 for the wood to build the forms ( most of which I can reuse )and about $445 for the concrete. I hired a couple of guys to help with the pour ( see my post about Bill" ).
The garage package cost $4200 w/ 9 ft walls, 16 by 8 insulated steel door, shingles etc. It did not include electrical, drywall, siding or an opener. The steel package was at least $1500 more.
BTW prices are in Canadian $$.