I'd guess three factors:
1. PNS has an actual discount carrier-AirTran. VPS doesn't, and the discount carriers tend to push down overall prices in a market.
2. VPS has some moderate scarcity issues. New routes have to be approved by the Air Force, and only get approved if they don't impact Eglin's primary mission. They generally do approve, but it's a layer of bureaucracity that does discourage new flights on existing routes a bit, keeps capacity a bit down, and leads to higher occupancy rates on more flights (and carriers feeling less like they need to discount to fill seats.)
3. Higher percentage of business travelers than PNS or PCB. If they're getting full fares from enough of those people, then less incentive to discount restriced tickets.
1. PNS has an actual discount carrier-AirTran. VPS doesn't, and the discount carriers tend to push down overall prices in a market.
2. VPS has some moderate scarcity issues. New routes have to be approved by the Air Force, and only get approved if they don't impact Eglin's primary mission. They generally do approve, but it's a layer of bureaucracity that does discourage new flights on existing routes a bit, keeps capacity a bit down, and leads to higher occupancy rates on more flights (and carriers feeling less like they need to discount to fill seats.)
3. Higher percentage of business travelers than PNS or PCB. If they're getting full fares from enough of those people, then less incentive to discount restriced tickets.