i get that this is a big issue to some people and yes it does seem a bit steep, but :-
if people are that adamant then why not buy the pie before hand/take it in turns with person next to you ?
its not just pies at the stadium that are going up in price.. EVERYTHING is..it wasnt that long ago a bottle of juice used to be well under a quid, now look at it
as has been pointed out the staff are largely kids...looking to earn a wee bit extra cash, they get paid pretty much regardless providing they turn up and arent completely stupid/thieving.
the club agree a contract with the caterers who are then left to run it..not being a lawyer but im pretty certain that they will be doing things to the bare bones within that contract to maximise there profits.. it is very unlikely that you will get a company doing it for the love