I think that all event rewards, as long as you get the achievement, should be purchasable via the Calamity Salvager sans those bought with gil. And if they are grind based, as in getting tokens, then they should just be 10-20k each from the Salvager as a trade off.
I also agree with OP in making them tradable. Some previous years items are still on the MB and thus in circulation. A few million gil in some cases, yes. But it's not $5.
