Unsubsidized PV is around €1 to €1.5 per Wp, IKEA offers 4200 Wp for €4321 right now. That saves at least €800 off my power bill.
A solar boiler starts at €2500 at minimum and easily goes up to €4000. It saves me €250 per year in gas. Or I could get a heat pump boiler for €1500 and save 80% of the €250.
Thermal solar was a thing when PV was stupid expensive but it makes no sense in ROI now, with PV you can power your hot water, home heat and everything else for about the same price as 2-3 solar heat collectors and a boiler.