Yes. A lot of.
I value the work the designer put into it. But you have to also consider all the variables:
1. This is not a one and done deal. If he had a single client paying that for 80 icons, of course it wouldn't be fair. But since it's a product that is created once and sold multiple times, the price shouldn't be decided by the hours of work or craft put into it.
2. These icons are minimalistic. There certainly is a craft behind this design choice, but compared to more realistic icon depictions (comparing to macOS icons for example), it takes far less effort to design these.
3. A lot of them have already been established. If you can simply take a pre-existing pattern and adapt it to your style, there's not much for you to do. Official logos of other companies and adaptions of app icons.
Don't take this the wrong way. I'm happy for the designer to have been so successful. I'm merely pointing out that the price is relatively steep in comparison with other icon kits of the same craft. But good for him that he was so bold to go with the price and get rewarded for it!