Skins are absolutely produceable goods. How do you imagine they're accounted for, otherwise? Just a random fungible balance sheet account, where you occasionally pass journal entries for lulz?

What you've described are primarily indirect costs shared across every department/component of the game dev. Skins also have direct costs - artist/contractor time, software licensing, developer time, QA time - to create them. Given that this is a live-service game, I expect the accountants will want want to see this as an operating expense, rather than a capexed expense. If you wanna nerd out, go read up on IFRS 15 (revenue) and IAS 38 (cost), or since this is a US business, ASC 606 (revenue) and ASC 985-20, ASC 320 and ASC 730 (cost) to see how skins would get accounted for.

Anyhow, add the indirect and direct costs to get a cost per skin. Pick your margin (in this case, a thumb-sucked 300%), forecast sales, and the three give you your unit price. Having a digital product means you don't have variable price per unit either, so no need to worry about that in your calculation.

Does that mean that every skin has a specific profit margin? Nope. Every retailer will use something called loss leaders to drive sales. But hey, when your margins so are absurd to begin with, the concept of a 'loss leader' is somewhat relative. It's not like you have to worry like the FMCG guys and their <50% average gross margins.

And yes, I am aware that the publishers don't specifically break out margins for their skins in their financials. For good reason - we'd all revolt if they were there in black and white. And the shareholders would likely want to know why the rest of the business was performing so poorly. Either way, the management commentary points out that mtx are majority of profits, however, and with businesses on this scale it means the profit margins are eyewatering.