They used to be low-cost _and_ open source. Now they're source available and not interested in anything but big clients. I was using Mapbox for all my clients before their unopen sourcing, and I tried reaching out three times to ask about options for one of my clients. It wouldn't have been a huge amount of money, probably a few hundred per month, but they never, ever reply. That client wasn't even using any of their server resources, they are 100% self hosted, it's just that Mapbox now charges even for using their client. Anyways, I was trying to give them money, and they wouldn't even acknowledge I exist. I switched that client over to Maplibre and never looked back.
The other thing that annoys me is that they've more or less abandoned all their open source repos without even as much of a notice in the README. All these amazing tools sitting there with open pull requests and no one responding for years. If they just did a clean break, put a notice on everything they weren't going to touch again, it would have been a lot better/easier for the community to fork and move on with their lives.