Make sure they put mesh in the concrete! (some didn't up here!)
Get recommendations from people about who they've used and check out the work.
My extra garage (6 x 7.2, plus roof extension etc) was over $50k (although that included extras, and concreting my barn floor too), and it's Brilliant (Skyline Whangarei). One of the competitors wanted an extra $5K for mesh(!), and another $5k to put a half-assed lean to between the garage and house, instead of extending the roofline, like I have now.
These guys integrated into the existing roofline perfectly, were super helpful and charged less. They actually made all the frames manually offsite after pouring the floor, so the roof is mm perfect. They were really into doing everything "right". Which was awesome.
It's not tall enough for a hoist or anything, but it does have 3 phase power (it was only about 5 metres of cable required).