What things used to cost! I found this 1973 BCal timetable in my "memory box". According to this calculator, £34.70 for a 1973 walk-up First Class return fare is equivalent to £327 in 2010 terms using RPI. A Moonjet return would equate to £125.
Full scans of the timetable linked here, about 1.5 MB each:
Sadly BCal were absorbed into London Airways ( trading as British Airways ) in 1987, a fate which also befell Dan Air and British Midland.