We just stayed there in March, and the cab ride to MK was more like $45 plus. Yikes. I did that twice, as we split up (one time I did the cab, then met DH at Epcot later; one time DH dropped me and our children off at MK and I took a cab back late at night). It was no where near $25. I think the ride back from MK was about $50 with tip.
If you want to go to Disney from Grande Vista, you really do need a car.