I would suspect 505.88 - price of the ticket you have. My guess is that the ticket you have has a 4 day face value, so I would suspect you will have to pay about 100$.
A gold pass renewal is (with tax) 505.88.
And, as an FYI. you can upgrade over the phone, contrary to what most people have stated. and what every cast member states.
I called yesterday, asked for Ticket Services, and upgraded my 6 day park hopper, to an Gold AP Renewal.
I called on Thursday to do it, and the cast member said sure, she just needed ticket services. Ticket services could not do it on Thursday, because I bought the ticket (originally) for someone else, with gift cards, and my name was not associated with having payed for it. They said I can upgrade it at the park, and or assign it to someone else no problem, but because it did not have my name on the payment method, i needed the permission of the person it was bought for to upgrade it. The ticket services cast member asked if I could three way call in with the other person, and have them give their consent for it to be released and use towards an upgrade. (No, I am not kidding)....
Saturday, three way called in with the other person (same number i dialed thursday), and a cast member told me it could not be done over the phone. I kindly asked to speak to ticket services, as they told me I could do it. (Not being sarcastic, I was polite on the phone). The cast member got ticket services on the line (took an additional 10 minutes). The ticket services cast member asked the other person on the call for permission to use the ticket towards my upgrade, which was granted. The third party was then told that was all that was needed, they were free to go, then the case member upgraded my 6 day park hopper to a gold pass renewal for the difference of like 50 bucks.