The most optimistic hope is that the government mandate will force enough demand that manufacturers can enjoy some economies of scale and actually try to compete on price. I don't think this will happen anytime soon.
I have one of these: https://cta.ch/en/private/products/ah-i-eco-innen
I got it in October so most of the time I've had it has been <10C. It's produced 806.3 kWh of heating for hot water and 6587.2 kWh for the floor heating. It consumed 302.7 kWh and 1801.4 kWh respectively, for a COP of 2.66 and 3.66.
That's why they're so great for warm climates though. The water heater also cools your house, especially as that heat is then lost down the drain. Everybody in the south should be jumping on these.