Well let’s assume the new lolita costume for female wizzard is what you want.
Let’s say I buy gatchas until I get it. I have a 50% chance of getting a premium cosmetic. By what we know so far 1% each (hats+lenses+dyes+hairs; since they said current costumes will be recycle only). So when they add the new batch of costumes I will have a 50%, then less than 1% to get it probably, but to keep things simple let’s say it’s still 1%. So on average I will need 200 pulls. (should be 100, but remember that only 50% of the times you get a cosmetic item).
Each pull is 30tp = 2,4€ (slightly less if you buy in bulk) —>2,4*200 = 480€ is what I might end up paying if I play and not stop until I get it (you can argue that I could stop sooner, and then recycle stuff to exchange for the dress, but remember that on release items will be ONLY gacha for a while, not on the recycle shop)
So what is the amount of silver I could ask for something that is worth up to 480€? Well, RMT bots spam ‘1M=2,4€’ on Fedimian. So I would need to charge you 200M+market tax = 220M for the costume just to break even, so you better start farming that silver.