You might even consider showing her this thread as another ways of convincing her that you're asking around to get lots of "yea or nay" opinions from unbiased strangers. It might show her that you're not just trying to fight her because she's your mom and you're trying to be a teenage rebel. Maybe she's afraid you're going to invest in these expensive snake morphs, then lose interest in them. Or not have the time for them once you go into college and either she'll be stuck with a whole bunch of snakes to find homes for. Or maybe she's worried that college will take up too much of your time, you end up not breeding/being able to successfully produce clutches and all your investments go down the drain. Lots of parents believe that snakes are just a passing fancy or a pet you get just to "show off", and don't understand why we have such a passion for the hobby, or why we would rather have "icky", scaly pets that are fairly independent animals instead of a fuzzy, cuddly pet. Every time I try and talk about snakes to my parents, they just can't understand why I own them. You should've seen when my mom told me to be careful not to get bitten, and I said "oh, I've already been bitten by one of my snakes. I mean, getting bitten is just part of being a keeper, so if it happens it happens." She was so confused that I wasn't worried about getting bit by a snake, and actually expected it. She doesn't hate snakes, she just doesn't understand what's so interesting about them versus a dog or cat.
Explaining to her not just the numbers side of making high-pricing morphs, but also that you love working with snakes and that it's something you genuinely enjoy will be another way to show your mom that you're making serious, thought-out decisions instead of just impulse "I want it 'cause it's cool" buys.