From what I read, you "have the reins" and it's definately wise to make him figure out how he can fund this expense.
Ohhhh, the burden - I remember it well. Having to "be in charge" made me more his mother than his equal partner. I hated being "his mother". It has a way of leaching into other areas of the marriage — but so many of us are in that role without even knowing it. In my case it nibbled away at any remaining respect I had for my AH. Nibbled away at his too.