For one or two people at $27.00 roundtrip each, Mears is cheapest.
For three or more folks, one of the towncar services such as Tiffany Towncar or Florida Towncar, the cost usually runs $80.00 round trip plus tip.
Tiffany Towncar will even include a grocery stop at no charge, so even for two people, if you stop and just get a few snacks, water, softdrinks, beer, etc. you will save money overall.
The towncars also provide the convenience of being just for you, no waiting for a bus or van to fill up, and no scenic tours of all of the resorts around Disney World.