I've had to do mine, my drivers side is working out at £24 for the square casing, and £34-£48 for the heated glass. Non-heated glass is half that. those are dealer prices with the case in primer, so will need to add paint on top of that.
Having looked at ebay I'd be looking at around £40 mark for both at the very least, so cheaper but not necessarily genuine or any good tbh. Careful of some of the glass if you dont go genuine, as some is just designed to stick on top of your existing glass. also, I think the genuine seat has a slight green tint to reduce glare. VW have blue tint I think, ebay might not have any - some didnt even have the extended vision portion on the far side.