and the airport shuttle boss selling me tickets then claiming not enough passengers so I’d have to either buy all the seats or pay a $25 taxi to drive ten minutes, forcing us to leave the airport to get a $10 taxi,
Never have I heard of or experienced in my 20+ experiences being required to buy all the empty seats in a shuttle. Sounds like you are buying a cheap colectivo ticket then expecting the driver to go immediately when you get into the van. If you want private shuttle service you have to buy a private shuttle ticket. The colectivos are shared vans based on filling as many seats as possible which means they may wait about 10 minutes or so but at some point they close the doors and go with what they have. There have been a few times where they left with just us as the only two passengers.
I've never put a timer on it but my gut says the wait has never exceeded 15 minutes. Hint: it ranges from 0.25 to 1 beers. Additional hint: there is a little bar by the shuttles to help you chill.