I installed floor heat in my shop using Crete-Heat panels. https://crete-heat.com/
I have 5 bags of 2" thick, 25 psi panels left over. This is 8 panels per bag, 8 ft^2 per panel for a total of 320 ft^2. New price is about $20/panel, I'd take half of that or $400.
I've attached a photo of what my floor looked like after the AL-Pex and the sand filler was installed before the concrete was poured. I've also attached a stock photo from the Crete-Heat website.
Edit: I am going to relist this once more on September 20. When that listing expires if no one has expressed any interest in these panels they're going in the landfill.