Paying for convenience/time is a fairly common practice in games today, even PVP ones in some cases. It’s not viewed by some as P2W because it doesn’t increase power just saves time for someone who has more money than time to spend on the game, and someone with more time than money and spend their time instead.

I’m not sure what I think about it in general (not knowing enough about the specific example you gave).

Personally, I am much more likely to buy unique ancestral knowledge real items than illusions, personally. I think it can be done in a fair way while still allowing some variety. Material costs and footprint per storage slots do need to be approximately uniform though, absolutely. As I’ve said, items that are too many slots for the cost/space are unfair and P2W, and items that aren’t enough are just a bad deal, and everything being limited to the same size and number of slots as a large chest isn’t a good solution either.

So what I’m saying: for 1 square footprint of T2 storage there will be 100 slots (approximately, just for example) costing 45 shaped wood and 15 iron reinforcement to build. Then DLC items can be carved out of that in any way that makes sense. This satisfies my desire for a unique and interesting item, while not offering any significant advantage or disadvantage for using said item.