IIUC, there's essentially a few vendors that own the vast majority of space in most airports, and the reason rents are so high, is because they outbid everyone

IIUC, there's essentially a few vendors that own the vast majority of space in most airports, and the reason rents are so high, is because they outbid everyone (knowing that they can charge $15 for a bologna sandwich)- not because the asking rent starts high. The problem is the business model - which could be considered price gauging - not the airport.