I know this may be a minority opinion among developers, but I'm ok with them trying to make money. And if the optimal way to do that is to ask 35% of the way through, then that's what they should do. I don't view that as a dark practice or bait and switch. I don't think there is an obligation to be super clear that there is a paid version.
It's something the owner should test, and see if it puts people off or if it converts better. Maybe it puts off 10% more people, but 30% more convert? Good on them for finding that out and optimizing accordingly.
We in the dev world expect way too much for free. Not that I complain when I find something for free, but people deserve to be compensated for their work also.