No 3x+ Clothing????? Make + size clothing to order!
Why not have larger size shirts made to order or made in small batches but priced appropriately to cover the additional fees.
If you go to a big name concert a tshirt is around $40 for any size, and I personally will sometimes buy more then one. Now, I'm not debating pricing. I'm not even sure $40 would be enough to cover the costs of made to order t-shirts. I'm just giving an example of what I've seen is top dollar for a t-shirt to make my idea more plausible.