I have the standard seats in my GTI with Leather (heated).
The side bolster (airbag side) and the seat base bolster is knackered as most are and the foam isn't "as new" as I can feel the seat base (must have been a right FB as the car has only done 39,000 miles).
Anyway - as I am getting the car back to factory fresh condition as much as possible I have my drivers side in to get all new leather on the bolster sides with new foam where needed. That is going to cost me approx £200-£250+VAT to do. So if you were to have all new leather on both I think a budget of £400+VAT per seat wouldn't be far off.
However, if it were me I would retrim them with tartan centres and leather sides or just sell them as is. Are they heated?
If I wasn't trying to keep my car stock I would be tempted by these - feel free to drop me a DM.