From Saratoga Springs Resort, our taxi was $28 there and $14 back. (The trip there is more expensive because of the way you need to loop around to get onto the highway. It's a straight shot on the return trip.) I thought $42 was a fantastic price for the round trip. ($50 with the tips.) We'd paid $30 (plus $10 tips) round trip for the two of us to Sea World on a Mears Shuttle the day before. The taxi was only $12 more, and we could come and go on our schedule rather than the Mears schedule. We also weren't crammed in as the last two of twelve people in a small van as we were on the shuttle. For a family, the taxi would actually be cheaper than the shuttle. (There's no additional fee for extra passengers. You just pay the meter.)
Last year, we took a town car. It was a luxurious ride, but also cost us $120.
Other resorts are farther away and are therefore much more expensive for the taxi. What you could do, though, is take Disney transportation to Downtown Disney, and catch a taxi from there. SSR is right next to Downtown Disney, so your fare would be somewhat comparable to ours. I believe these are the closest places to Universal and Sea World on the Disney transportation network.