How do autistic people handle haggling culture?

I have pretty much never haggled in my life and every service worker I've interacted with has no authority to adjust prices.

(Actually when it comes to art commissions I seem to severely undersell to end the interaction as quickly as possible)

Honestly seems nightmarish and I feel like I would get charged $50 for a box of cereal regularly. I already feel like I get charged more for things because I hate shopping around for a quote (usually go with the first person I call because I hate rejecting someone after I've asked them for a quote)