Large overheads, but the VAT is collected and not theirs.
Small cc Skoda VW Engines have had, 2.8, 3.2, 3.6, 3.9, 4.2, 4.6 and 4.8 litres capacity and the same charge was made with the old Fixed Servicing.
As were the spark plugs be it 3 or 4 cylinder.
There was a while where the Fixed Price excluded 1.0 cc engines, but that did not mean all got the serving cheaper.
The Old Minor / Major, then Minor or Interim & Major took the same money as a 2 year major as a @4 year major which was a nonsense as a Air Filter, Fuel Filter or spark plugs were not done at 2 years old.
But then it really was 'Fixed Price' on cars 3-10 years old, but places were taking the pith.
............
It was not Customers responsible for Defeat Devices and VW cheating, or the number of recalls & TPI,s and still them having poorly built or prepped cars back in making workshops bust doing warranty work.
Pre 2020. This system was flawed as far as what customers paid.
A technician or fitter could decide not to fit consumables, or even check if a air filter was needed, or spark plugs yet people paid the same not to get them.