Definitely varies. National teams typically charge similar rates even at smaller events because they provide the same level of service. And not all local or regional shops offer arrive and drives.
That said, a lot of single day club races I’ve seen 206 arrive and drives for $250-$300 including a floating mechanic (aka a helper if you get in a bind that just roams the tent).
Biggest factors in this are the cost of engine hours (for example, a tag motor that needs to be rebuilt every 5-10 hours averages out to $100-$200/hr in cost, and you put about an hour of run time per raceday), and chassis depreciation. Chassis are just like cars in that their biggest depreciation is in their first few weekends. If you are doing an arrive and drive on a 1-2 year old chassis, the team may be able to charge you less than if you were to rent a 0-3 weekend old chassis.