My D visited literally dozens of schools. She and I took 3 or 4 multiple day trips, her Dad took her to see 3 schools that were bunched together (upstate NY) and an aunt took her to see another 3 schools bunched together (ME) in a different local. Only one trip required a flight and that was PA…we flew into Scranton, rented a car, drove down to BWI and flew home from there. We made it a vacation and spent two days in Amish Country and some time exploring Gettysburg 
We both enjoyed our trips and tours very much but yes, it can be costly and time-consuming to try and visit all the schools they are interested in. The only school she applied to (ED) but didn’t visit was 18 hours away, pretty much a crapshoot so we didn’t spend the $$ (rejected as expected lol).