His work often gets used, without permission.
Sometimes commercial entities ask for permission but won't pay.
Other times they offer the smallest, and least enticing, of carrots. Read how he turned down a t-shirt from a Kansas City company putting together a proposal to construct the metal outer shell for the Barclays Center.
It is a testament to Collins' professionalism that, whatever his position on the project (and he's clearly an opponent) his work is such that metal companies in the Midwest might want to use it.