I personally have an unwritten agreement with my wife that family money is "family money" so what I make from my regular job goes to "the family" and I don't use that in any way to buy cards. That being said anything I make selling things in the hobby on the side is mine to do with as I please, so if I sell items on ebay or to a forum member she doesn't expect to see that money in our family bank account (I do often spend "card money" on them but it isn't expected.) We have never really argued about money as it pertains to how much I spend on cards because of this agreement. This wouldn't work for everyone as all wives are not created equal, but it works for us.
There are members on this forum that spend anywhere from $0 (as they are mainly observers and not really collectors anymore) to those among us that have nearly unlimited funds they can utilize on a whim (enough to buy the T206 Wagner several times over). The diversity on this forum is something that makes it great!