Elia's article: Convert Clothing for Additional Yuletide Item Exchanges!
The Yuletide Exchange RatesLevel 1 Yuletide clothing piece gives 10 x 1st Calendar Page + 20 x Sepulcrum
Level 1 Yuletide wings give 25 x 1st Calendar Page + 40 x Sepulcrum
So basically wings is definitely not interesting because this says that they value wings as 2.5 clothing pieces, when wings are actually worth 5 Fashion Cores or 5 clothing pieces. So a more fair exchange for wings would have been 50 x 1st Calendar Page + 100 x Sepulcrum based on clothing times 5.
Yuletide Exchange Trick Analysis TableDecision is on the right side and you can enlarge the picture by clicking on it to see the full resolution image.
Clarification on the Yuletide Wings Decision
Basic wings are basically worth 5 Fashion Cores or 5 clothing pieces, so 39 clothing pieces is 8 times more the price, which is why the decision is still "no". Additionally you might get the wings from the drops. However, if you have tons of level 1 clothing items and already high level cloths on you AND you were super unlucky not to have the wings drop then maybe it is a good idea to exchange for this. But probably not :)
Clarification on the Owly Card Decision
120 clothing is about 35.8k balens vlaue, which is almost the value of a level 7 clothing piece, so then you have the question if the mount is worth 35.8k balens to which few players will say "yes" but most will say "no".
Yuletide for Sepulcrums
So we already saw that exchanging clothing is not interesting for most of the exchange options, however we have to keep in mind that you also get Sepulcrums for the exchange. And here we have the question:
Is it worth converting clothing into sepulcrums?I would say that we earn sepulcrum every day, but clothing we do not, so converting a more rare item into a more common item I think is not worth it.