It’s because he has been living quietly for a year and the fact that he missed out on whole 8 years says a lot so he doesn’t fully know about how things work as of the current timeline. You could say he’s like a grandpa who is yet to know how to handle a phone.
According to the novel, the situation between 8 years ago (when MC disappeared) to today is too different, the MC haven't adapted yet.
About the pricing, the MC did try to find out but the information is closed and exclusive for Hunter so the MC just guessed by the price 8 years ago and add on a bit more
I also want ro add in that the MC was an active hunter during the days when he was really young and the world around was just an apocalyptic chaos. Without spoiling anything you can think of him as being less of brain and more of the brawns type. The world is a little more pragmatic here too, just because they have super strength, they don't just go around running and hopping through buildings like many hunter novels/webtoons with OP MCs. I said that as an example to put emphasis on the fact that it's not a novel like Solo Leveling and so on.
3 stars for now. Because I'm quite peeved by the fact he's an s rank hunter but he finds himself getting into these situations without properly checking? Or I'm just used to those typical s-rank hunters who are too good at everything? Anyway, regarding that magic stone he purchased? I thought he searched it online about the details? Pricing, their value, etc.??