Some real nonsense being said here...
How is it nonsense? There is no space for an ILS on 03 and the transport links are not good. This remains to be the case even if Biggin could handle ticketed flights. All of these issues would need to be resolved not just one of them.
It's not much more than we pay elsewhere these days, landing fees are comparable to Shoreham, Redhill, Fairoaks, Southend, Blackbushe, Le Touquet and plenty of other popular GA destinations.
Listing other expensive airports doesn't really make a case for Biggin not being expensive, though I will say that of your list Redhill and Fairoaks are on the better end of the spectrum, particularly if you join the flying club at Fairoks. Biggin and Southend are expensive, and there's no two ways of looking at that. No idea about Blackbushe or Le Touquet, but lets not forget there are still places around London where you can land for £10!