It cost about $20 and we didn't pre schedule it, we just walked out of the resort and there were plenty of taxis lined up and someone at the bell services stand just threw up his hand and mentioned a large cargo van over for us. The driver got out and got a little step stool out to help us get in and then another member of my party put the mobility device in the back where the driver instructed him to put it. When we got back to our resort the mears driver did give us a card with a number to call if we needed to schedule a taxi, it also had info about their app too on it.
We had no problems, we took the nears taxi more than once and it was never more that $25 anywhere we went on property (we only used the taxi for resort to resort transportation, not to a park).