If you get onto 417 at Sanford from I-4, the tolls should be around $7.50 each way. We bring two rolls of quarters.
We like taking Exit 3 because it takes you through the big main gate/sign so it's worth the extra toll to us. Just make sure if you take Exit 6 that you go straight and don't turn right to the DTD entrance. No matter what time of day you'll sit in bumper to bumper traffic for a while and get SO impatient.
We LOVE 417 and highly recommend it.