Agreed. While you're not paying for using the product by buying a software license, you're often required to buy tokens (get it?) in order to use the product. The developers benefit from the increase in token price, because they often own a lot of those tokens.
Not that this is necessarily unethical, but it's good to know the incentives behind this.
>> FOSS developers
I don't think it has something to do with FOSS but rather with blockchain developers. Most projects have nice landing pages but very vague messages.