Most people can get by with 2mg injections, so that means you would get three from every injector. A few seem to need 3mg, which would of course mean two aborts per injector. (Or you could ask for 3mg injectors, which some doctors are willing to prescribe, or even for a vial of sumatriptan and syringes, which some people can get). You would have to figure out the cost difference, but I'm guessing that one is paying a lot for the useless autoinject mechanism itself.
Your doctor's logic for not prescribing a preventive or trying steroids seems odd to me. I'm not sure how you would get things "under control" without a preventive. For most people, the steroids only provide relief while they're taking them (if then), so they are meant as a "bridge" to give the preventive time to take effect.
It's also a little hard for me to know how much his "perception of the severity of the problem" actually matters, He's gonna prescribe what he's gonna prescribe, and his sympathy is worth very little to you. People here all know what you are going through; unfortunately your child probably gets it, too, at some level; but practically nobody else will ever really understand.
Here's some basic info about LSA, but you should check back with us if you decide to go that route. There is typically no "trip" at all with seeds. But of course no substance is assured to work, and you have apparently already found one that does. https://clusterbusters.org/forums/topic/684-5-lsa-seeds-of-the-vine/
You might not be aware that psychedelics don't work while you are using sumatriptans or steroids. The standard advice is that you have to be "detoxed" from them for five days before psychedelics will work. There is not 100% agreement about this, but it's what the bulk of experiences say.