I own and like the steam link, but the reason they don’t sell it anymore is because the steam link app is on most smart devices now, and if your TV doesn’t support it, you can buy a streaming stick that does for like $30, give or take depending on sales. And those devices are more portable (less wires) and more versatile than a steam link.
Any competitive price for the steam link would be less than what Valve can produce them for. Weren’t they selling it for $5 at the end? Pretty sure I picked mine up for $10 or less. Steam can’t show ads to subsidize the price of the hardware like every other smart device does.