Sorry Olivia, don't normally do this, but I'm gonna play devil's advocate this time. I do happen to think your parents have a good position, and let me explain why.
First, yes, they may not understand trans completely. That said, I personally wouldn't pay for something I don't completely understand either. While it may seem a little distant from support, I'd say lack of understanding is probably part of it.
Second, look at trends between parents and children today. I mean, there was just that goof of a teen in jersey who sued her own parents for "not financially supporting her." Families, sadly, are blaming each other for things more now than ever. Reckless irresponsible children (even adult children) aren't taking responsibility for their own actions, and look to blame others. A common blame is on parents for not "being raised right". So, your parents position is understandable. They aren't disowning you, but they wouldn't want you to do that to them, heaven forbid something goes wrong.
While we may not be understood well, it usually takes someone else to make us realize that our trans education is years ahead of those we come out to, and twice as focused.