I will give you a well known comparison. Years ago (appx 1995) I worked with Martin Clark (ex Partick/Falkirk) who is John Clark's son (celtic lisbon lion/kitman) Martin told me for a fact that we were making more money than his dad was at Celtic. (we were on around £250-300 per week at the time). So basically, Celtic were (and most probably still are) paying their kitman around the standard tradesmans wage. Nowadays I would expect that to be around £25-30k per year.