Depends what they have done, if you think about it, it is possible to bleed a HFX in around 10 mins, inc getting everything ready and packing away. But lets take the fact that HFX'9s are now an old brake, most likely to be over 2 years old as that's when they got replaced by the Stroker.
So this makes a 'quick bleed' into pad removal, caliper clean and inspect, lever clean and inspect, pump the caliper pistons out halfway, clean them, reset, pump again, clean again, reset. Check all the fixings, bleed, be amazed that a brake containing 50% water and 10% mud can still work at all, bleed through again to remove last traces of said gunk, refit pads, check rotors are straight, chances are they won't be so get out the truing fork and spend 5 mins an end trying to sort out the results of repeated shed stacking/car packing, pump up the brake, and align it.
Not all of this needs doing all the time, but often does. £20-£25 an end, with the time taken, is pretty much bang on. After all, if you took your car to a garage saying "my brakes are all squishy" and you found out that rather than checking your braking system and finding out WHY it let air in/oil out, and just bled it through and sent you on your way, there would be daily mail style outrage at these pirates!
you can't put a price on safety 😉