It's not so much that it's a catch 22, its that there's no financial incentive for them. TVs are a low margin item already, and Samsung/LG get their margin by being brand names and advertising fancy features.

I doubt they would meaningfully save money over investing in DP, and the opportunity cost is greater for them to spend that money on the next "Frame" TV or whatever.

LG, Samsung and Sony are the only actual panel manufacturers and they probably bake those license fees into the panels they sell back to HDMI Forum.

May be, but by not solving the problem, they become part of the problem, even if they aren't part of HDMI cartel directly. So it's their fault too problems like above happen.