they do have 2 sets of drop outs listed now – one the original for £15 each and one the ‘new’ CNC ones for £20 each and also come in red.
I can’t see why the geared silver CNC ones are £5 more than the original ones but maybe they are different but the SS ones appear to have slots machined in them.
TBH I think On One have been pretty poor with the drop outs. They were originally £10 each side but now £15 and £20 – that is a stupid price IMO as you are looking at £30-40 for 2 chunks of metal. Yes replaceable hangers are £10-15 but they are stupid too.
I also think they have completely missed a trick and should have made the SS ones with a built in tensioner that screws in from the front to tension the wheel. tbh you could very easily add this by drilling through the drop out and threading it or using a nut.
PS I think they missed an even bigger trick that they could have made a drop out that moves the caliper with the wheel like you get on some frames.