We paid less than 60 a pop for our rad heads, and something like 180 for the EVOHOME starter kit (controller, boiler relay, one rad head).
The two year battery life is bullshit, obv - especially for the shitty in-box ones. Its started complaining about some of them after less than 18 months. We've an accidentally-accrued huge pile of Duracell's to use up but then eneloops will be going in (2x AA per rad head).
They use a custom protocol at about 811MHz and the 'put it on the ibtarwebs' box is another hundred quid we didn't want to pay because fuck off a hundred quid just so I can mess with it when I'm not even there.
And the scheduling is traditional 'designed by a heating engineer trained in the Dark Ages' stuff rather than the lovely Nest learning business. But it does the bit I want. But not a water schedule on a combi, just a kit for tanks.
I remember getting to around £70 a head, but at the time you need a wireless thermostat for each room which pushed the price up.
I'm not sure I see the value in having that level of control, I have those 1-5 manual knobs on each one of mine and we manage it with those, also have my 2 year old son turning them down all the time this winter
Will be giving the topic of heating a deeper look next year as our house plans go in and I want all the boilers etc in the garage. Also has the house will be gutted and underfloor heating will have to be the solution in the open plan kitchen\Living area so the heating will need looking at.