If USAir could charge another 1.50 for a ticket, they would. But they can't. Any extra fee equals a reduction in passenger traffic. That's a loss of revenue for USAir, which means they are paying for whatever the local yokels decide to spend it on. Like an unnecessary runway extension.
Of course they could. And they will if they want to keep full planes and service (see our aircraft retirements and no fleet plan) into HH. If you believe that people who already pay a premium for a ticket onto the island so they don't have to make the 45 minute drive would notice the buck fiddy then you're mistaken.