Pay per CP12 check hasn’t increased in 15 years

I have 45 years in the gas service engineer trade: 30 years at British Gas and 15 years contracting. However, the price to carry out a gas service and CP12 check per property has not increased in 15 years, despite more factors to check for the record.

Is this fair? The pay ratio is five times less per job than the private sector and still around £20 per property to service or inspect for CP12s.

My agency even takes a cut on standby pay and CO alarm fitting incentive on top of the mass they earn per job/hour!

Market median pay with union and HR negotiations is missing from self-employed subcontractors and inflation is not taken into account. Any ideas, fellow Gas Safe engineers?

Name withheld