My memory is the prices weren't way in excess when compared to Uber XL rates. High Minnie Van rates, compared with basic Uber fares, suggest the demand for Minnie Vans should be low.That's all true, but Disney was also charging prices way in excess of what Uber and Lyft were. I have a hard time seeing how they would have been losing money. It could be possible that the Minnie Vans weren't making enough money for Disney to justify keeping them around.
Uber and Lyft are losing money. Uber and Lyft don't have any of the expenses in running a car service; vehcicle cost, gas, insurance and labor. operate. Uber and Lyft drivers aren't being paid anything close to what's needed to operate.
Rates charged by a money losing company with lower expenses gives us no information as to how much Disney needs to charge for Minnie Van servce. A better, starting point, of price comparison is what does Mears charge for towncar taxis offered at the Swan Dolphin.
Everything I've read suggests demand spikes, dramatically around park opening.