I have spoken with about 40 architects and general contractors / main contractors / construction companies. Unfortunately, with the architect, you only get a rough cost estimate in advance (e.g., about €340 per m² of built-up space). With the others, this sometimes comes as a complete fixed price.
I am a fan of that because the costs are clear beforehand.
At the very least, you can get an overall idea through several offers / conversations.
Asking costs nothing.
Regarding the general question of whether to choose an architect or a main contractor, there are also numerous threads and long discussions here; just try using the search function in this forum.