The costs of employing someone are more than just their salary; need to include Employer's National Insurance at 12.8%, employer's pension contribution (variable) at, say 6% plus the costs of any other benefits agreed in a contract (this could include eye tests, staff welfare, all sorts).
This means that, five pilots would be earning around £44k per annum each; that's about right. The observer's amount of £110,000 is bizarre as each aircraft uses two observers and therefore I would think there should be around ten on the books!
Very few of these figures ring true and, although I don't doubt the OP had used his rights under The Freedom of Information Act (again!), either the information provided is incorrect, the OP asked the wrong question or has misinterpreted the answers.
Cheers
Whirls