Have you specifically decided on steel garages or are other construction types (concrete, timber frame, etc.) also an option?
Basically, you have to break down the offers and compare them precisely. Therefore, it is difficult to compare prices directly.
For example, I have an offer from Garagenrampe (02.2019) for a double garage CH90 including installation with 2x sectional doors Hörmann, fascia, increased roof load (300kg/m2), approx. 5.8x8.7m, including downpipe, electric drives, 2x door opening, side door for 14,799 EUR (list price was 17,000 EUR).
Offer 2: Großraumgarage München 90. 1x large door, otherwise as above for 15,359 EUR (list price 17,500 EUR).
For comparison, concrete prefabricated garages were at least 50% cheaper. Due to my increased requirements, we will now have a garage built with masonry. However, the prices there are at least 100% higher.