I did the same when I got the email from Yahoo... Absolutely insane price increase.
Moved them effortlessly to another registrar WELL BEFORE the due date so there would be no confusion.
Word of warning -- after you move them from Yahoo, be sure to CANCEL your accounts for those domains on Yahoo. There's been several posts here and on other forums of Yahoo still charging for domain renewal after the domain has been moved.
The code you need to move the domain is already on the domain listings in your Yahoo domain account so you can move it immediately.
Good luck and hope this helps