First let me say that BUILDING MATERIALS ARE MUCH HIGHER NOW THAN 8 YEARS AGO! My Wife and I are going through a Home remodel right now and believe me it is expensive! VERY EXPENSIVE! All new kitchen,walls being torn out,new sheetrock,new plumbing,flooring etc. Also about 4 years ago I had my 24 X 40 metal building built with full insulation,central air and heat and it was around $14000.00 finished! Today I would expect this building to cost in the area of $24000.00 or even more due to price increases in Concrete,steel and other related materials.As one member said there is too much difference in prices on your quotes! Someone is not on track with the bid.I also would say that the HIGHER estimate is more realistic! Would not hurt to get another bid and make sure all are bidding on the same thing,size,type of materials used,thickness of concrete,electrical etc. You can also get a book called a Cost Means Construction book and do a cost estimate yourself just for peace of mind.It is something I always do on any project.Also find out from your contractor if they have references on previous garages built in your area, and contact those people to see how everything went using the contractor and there satisfaction with the work,contractor and finished product! Us Mopar people got to spend our $$$ wisely so we always have a little to spend on the MOPAR PROJECTS!
Bobby