I really identify with your post. I also have some issues understanding what the logical price of things should be, but when shopping I tend to buy the same things repeatedly so I just compare the prices to the last time I bought whatever it was. However, I don't understand other financial things at all, and I think it is related to autism in my case. A lot of aspies have particularly good logic/maths skills so those AS people may not have difficulties because those skills compensate (or they may even be particularly good at it), but I suspect the right brain aspies may struggle with this. I think it is related to difficulties with executive functioning and failure to absorb social norms appropriately. I've never met any of the expected milestones where money is concerned.
I am not stupid - actually I even did fairly well in high school maths. However, I can't get my head around things like tax, benefits, bank accounts, car costs, and so on, and I have been expensively stung by this difficulty on multiple occasions (I lived on my own for years without any idea what council tax was until I was sent a very large bill, have been overpaid and underpaid tax credits multiple times because I had such difficulty keeping on top of them, and several times have been charged money by companies for services I didn't use because they had set up recurring payments in my bank account without me understanding that they had done it). Staff in banks appear to me to be talking a foreign language. I am able to manage things now, but only because I have made my financial life so simple - I have no car, no insurance for anything, nothing I spend money on regularly. and my only recurring monthly payments are my rent and internet. I couldn't possibly manage to live the way most people do in this society (phones, cars, direct debits, mortgages, insurance for fifty different things, what?) and understand what was going on. It completely boggles my mind how they do that. And I am nearly frustrated to tears when I have financial forms and things to fill in.
I understand the suggestion of studying the subject, but knowing what the names of things mean and what they are is the smaller part of the problem - the bigger part is an inability to cope with things like filling in forms, deadlines, organising, multiple things going on to keep track of (like lots of things going in and out of a bank account), the complexity of the way government systems work, and so on, all of which I find so confusing that they cause me a brain crash. It may be related to ADHD in addition to autism, I'm not sure. Either way, you have my sympathy and all I can suggest is to simplify, eliminate or automate everything you possibly can. I find those things help, and I just nod and smile when people talk Dutch to me about financial things!