Oracle, now let's do the math. These regional routes may at best raise about 40 pax per sector on a good day. So....small second-hand 50 seat jet for $5 million using 1000 kg fuel per hour versus bigger second-hand 90 seat $5 million jet using 2000 kg per hour. Add nav charges based on weight, third flight attendant on the bigger machine.
OK, a 50 seat turbo prop could be cheaper still, but the fickle public will always go jet given the choice.