The reason colleges cost so much is that they've expanded their administration, facilities, and sports programs to soak up all of the available loan money.
I went to a state school that focused on STEM. The acceptance rate was low, class sizes were small, and the tuitions were reasonable. The buildings dated from the 60's. We didn't have extensive athletic programs, and our gym was falling apart. The school didn't spare expenses on things that didn't contribute directly to education.
We still had access to full machine shops, doppler radar installations, flow cytometers, BSL-3 labs, electron microscopes, wind tunnels, robotics facilities, and a boat load of really cool stuff. But it certainly didn't feel like an ivory tower.
Though our school wasn't losing money, the state board of regents decided to merge it into a much larger "liberal arts" school. This was done so that it could hit the student body requirements in order to qualify for building its own division I football program.
They built lots of fancy buildings for their dance program and theater productions. I can't even count how many stadiums and sports facilities they've constructed - it feels like two dozen! They're also purchasing lots of expensive real estate to enhance the size of the main campus. Meanwhile tuition has quadrupled and fees have gone up 1,000%.
It's bloat. That's why everything costs so much.