Though like many people, I dislike the idea of consumables. I'd totally be down for a $2 perma dye or something.
That's excactly what I was talking about. Make the dye cost 2$ but be permanent, although personally I think price should vary between 1$ and 2$ (just as now the cheapest ones are 20 cents but more interesting are more like 40 or so).
Perhaps 1 unlimited dye every 3 levels, so you still won't be able to collect all the dyes without paying.
If you want to keep the usable dyes (which for me is questionable) then it's good idea to squeeze those permadyes to be the prize for the levels that currently have no prizes.
I would love to be able to exchange one dye for another of equal value... I need more spring green... I'm out.
Well, how about taking this idea a bit further - how about being able to "return" every item to the store for 20-50% of it's worth to use in the store? Of course the idea of returning an item for one of the same (or less) value is really cool but I don't think Muse would agree to do it.