If you’re talking about the same buses Disney uses for resort transportation, those buses are not designed to carry luggage and won’t hold 100 people on a run from the airport to WDW. It would be an awesome idea to bring DME back though.This was a stupid decision. Seriously, just use the many busses in the fleet and charge whatever it costs +40%. You can't tell me this was some kind of impossible task.
Lots of people would use it still because Uber/Lyft can get close to $70 one way.
Load up a bus with 100 ppl and charge them $20/each adult and kids are free. This would get people to use it FOR SURE and you'd likely have 50 adults per bus for around $1,000 in revenue. They could optimize the routing somehow to run fewer busses. It's just stupid. Hell, I'd fire up a bus service if I actually needed the money.