In terms of the Blues, T-Birds and Fleet Week, sure they cost a fair amount of money from the DoD but they have an inherent mobility that comes with them that other units do not. Ships are going to sail regardless so why not have them pull into a local port for a couple days for some fun. They do it overseas enough anyways. For the Blues and T-Birds, yes they are extra but are already established units and moving them from city to city is easy and they go to established airfields. As for a parade through DC, a very busy city with a lot going on on even the quietest of days is something different. Flyovers are easy, but moving tanks, personnel and weapons systems aren't and it'll take a lot of coordination (just think of the security alone). We already have enough display of forces and recruiting tools, we don't need a massive parade through the nation's capital.