While it could be that your usage data is collected and worth that much to them; the far simpler reason is simply both how competitive the "normal" TV market is

While it could be that your usage data is collected and worth that much to them; the far simpler reason is simply both how competitive the "normal" TV market is, and how much you benefit from economies of scale. Even if your usage were worthless, a smart TV would likely be considerably cheaper. Also, don't overestimate the bill of materials for a smart TV. Even a "dumb" TV almost certainly has silicon brain simply for controlling the settings UI and various other functions - that's cheaper than buttons, and remotes need something to talk to, so really, a smart TV simply means "a slightly fancier chip" - but still a chip that's several generations old by smartphone standards. It's not going to be a significant extra investment for the producer.