This is classic Ryanair wording.
When they cancel a flight and say you can “choose a new flight for free,” what they really mean is no change fee. You still pay the full fare difference to whatever the new price is now.
So if your original three tickets were 350 € total and prices for the new dates have jumped, you’re basically repricing the whole booking at today’s rates. That’s how you end up staring at a 450 € charge and wondering where the original money even went.
Your 350 € doesn’t disappear, it’s just being credited toward the new booking, and the rest is the difference. But yeah, it feels misleading because “free” sounds like you won’t pay anything.
In a lot of cases, refunding and rebooking separately actually is the better move, especially if the wallet credit isn’t useful to you. Ryanair’s rebooking option only makes sense if prices stayed similar.
Annoying, but unfortunately very on brand for them.