This is exactly like the issue when you want to support a company or a person by buying their merch, but you wouldn't wanna wear the merch in public. too embarrassing
I think the money that dacon makes from the webstore will suffice
I feel like the key with merch in general is to make designs that aren't too flashy that a lot of people would like. I feel like sweatshirts with just the ManaCube logo would be cool, I'd buy that. But putting slogans and other things on there would be over the top and it wouldn't be very successful. The more simple, the more broad amount of people will be interested.