Dealership ripped me (32F) off, boyfriend (37M) doesn’t care. How can I get him to care?

I just had the most frustrating moment with my boyfriend of 3 years. So much so that I am re-considering the relationship as a whole. He just doesn't seem to understand why what he said was wrong.

Boyfriend (37M) is very passionate about cars and takes his cars to a very specific dealership. I meanwhile know almost nothing about cars besides basic maintenance. I used to get my oil changed regularly at a chain oil place, which my boyfriend found out about and told me why they were so bad (something about their lifts can damage the frame?) And told me to stop going there and instead start doing my maintenance at the dealership where he takes his cars.

Time for an oil change, I brought it in to his recommended dealership, and long story short, they tried to charge me $300 for the oil change and gave me a check list of urgent things I needed done to my car (new spark plugs, all new tires, all new brakes pads and rotors, all new filters) which totalled over $2000. I negotiated at the payment window for a better deal on the oil change, because I was used to paying more like $50, but they explained how my car needed a special type of filter and they used all synthetic oil and that the $300 was correct.

I got home, told my boyfriend what they charged me and showed him the list of repairs they suggested I come back for. He said that was insane and that his oil changes there were $40. We compared my bill to his, and they used the same amount of oil and same number of hours of labor, its just his labor per hour was $50 and mine was $400. He also checked my tires, brakes and spark plugs and said none of them needed replacing.

I was so pissed. I told him I suspected they were overcharging me based on the fact that im a woman. He replied “I dont think thats the case, its just a stupidity tax. They saw that you didn't know anything about cars and charged you accordingly”.

I told him I'm never taking my car there again, and urged him to do the same, but he said no that I could do whatever I wanted but that he planned to continue taking all his cars there. This lead to an argument, I asked if he was OK supporting a business that took advantage of people. He said it didn't matter to him since he was car smart and knew enough not to be ripped off. I told him that I felt insulted that he indirectly called me stupid, and his reply was “well, do you know anything about cars? No, so you kind of are stupid in terms of cars. You can fix that by learning more about cars”

I feel insulted that he called me stupid, and upset that he took the side of the dealership, upset that he won't admit that this was a sexist move, and just overall I hated his response. How do I navigate this?