I think others have posted here they did have to buy non-expiring MYW tickets, as the old tickets were also non-expiring.
The old
ticket prices are available to CMs, but hard to get from my experience.
What happened to me:
We renewed our FL PAPs December 31. (Our renewal date was a week later.)
DH happened to look at the back of my PAP the next day and noticed I was sold a child's PAP.
Later in the week we went to Guest Services in DTD, paid the extra for an adult FL PAP. I thought I had a corrected PAP.
Later, I noticed my new PAP had in incorrect expiration date.

And I realized I was charged the NEW (increased rate).
While my DH was running the marathon a few days later, I went into MK City Hall (where we originally renewed our PAPs) and explained the situation.
The CM was very helpful and corrected my PAP expiration date by issuing me a new pass.
Next, the difficulty of reimbursing me the $17.03 price increase I should not have been charged at DTD Guest Services.
The CM nicely asked another CM what the old price was.
That CM rather

wanted to know why.
The CM helping me explained the situation to her.
The other CM's reply -- I don't know.
The CM working with me called someone to get the old ticket price information.
Why did she want that information, they asked?
She had to go through the story again.
They finally gave her the cost from December.
From this experience I figure the old ticket prices appear not to be information CMs can readily access, or is easily given out.