I had an alarm fitted by an alarm co engineer as a Homer. Works for a major
alarm/security company. He charged 300.
Fitted 2 keypads, 2 PIR's, 3 sets of door contacts and a window shock sensor
in a 3 bed end of terrace.
Its not the parts you pay your money for though, its the time taken to fit
it and do a decent job of hiding wires etc