FWIW:
https://www.homeadvisor.com/cost/garages/install-an-electric-vehicle-charging-station/
Personally, I wouldn't even mention the fact that you are wanting to charge an EV. Just get quotes for an electric dryer (for 30A circuit, if your planning on using an EVSE operating at <= 26A) or for an electric range (50A circuit) - tell the person that you are thinking of boxing in the garage and turning it into a suite - whatever
I think you'll be surprised by how much cheaper the quote will be, compared to when you ask for a circuit for an EVSE for electric car charging.
I'm not saying that there is wide spread intentional scamming among electricians, but I think that a lot of electricians who have yet to do their first EV charging install are padding out their quotes, in case there's a bit of a learning curve...
I'll be surprised if it takes more than 2-3 hours to complete the job, so $200 - $250 for labor is fair. The 6/3 NM-B wiring should be less than $3 per foot, it sounds like your run would be around 50ft, so the cost of the wiring itself should be less than $200. But if conduit is needed (ie not run inside the walls) then the material costs would be higher. So, the material cost doesn't sound too far off.
Assuming a generous $100 per hour, the quoted labor cost means at least 6-1/2 hours of work is anticipated - sounds excessive, but you'll have a better idea than us how challenging the "run up into my attic and over about 30 feet to the garage" run might be...