You need to remember that for BIH to operate ex Penzance they need high overheads, large site, staff, fire cover etc. This results in the fairly high prices of S61 flights.
The fuel cost for operating flights ex NQY will be higher, however the other costs would be much lower as BIH will dump the staff and outsource the entire operation to NQY as the handling agent
I still think that BIH could benefit from some sort of interline agreement with BE to allow connections onto the IOS
cs