I can go back 30 years, indeed longer than 30 years, when I worked for a CWL based operator, thereafter I worked for other operators who would operate thru CWL and NEVER did I hear a single reference to CWL being expensive.
Airports all have their scales of charges, landing, navigation, parking etc. and I'd imagine that the regional airports, so to speak, recommended retail prices of these charges are all pretty much the same and if CWL has been historically overpriced, when compared to other airports, then why were such operators as Air Cymru and IEA basing their fleets in CWL, why were Manx Europe so keen to move in, I recall that BAC Express pretty much had a Shed or two based their, Norman Aircraft manufacturing crop sprayers there and thriving flying clubs to name but a few.
It is a rule of thumb of business that the greater volume of something that a business has then they can afford to let a percentage sell for a discounted price, that could be a hotel and rooms, an airline and seats or indeed an airport and movements.
What may have well happened is other airports, BRS perhaps, have reduced their charges to attract the volume, BRS's geographic location would permit them to do so, whilst with a lesser volume not permitting them to do so CWL got left behind, not a case that CWL have increased their prices but others have been able to reduce their prices, kind of alike the supermarket vs the convenience store scenario.
CWL doesn't have the volume to permit them to reduce prices when due to geographic location they're not going to reap the rewards of doing so, somewhat amusing though to repeatedly read complaints that CWL is too expensive whilst reading counterproductive complaints that CWL is a drain upon the taxpayers of Wales, you people can't have it both ways!
BRS were lucky to source and appoint obviously the right person for the job as MD back in the 1980's, perhaps one day CWL shall be so lucky also.