Well, to be fair, these numbers seem meaningless without any context. I'll give extreme examples. In DC, the median house price is near half million dollars, the mortgage on that can be around $3,000 month, and if you add in all the other costs, you could easily be spending $5K a month to maintain a household with all the modcons.
So if you offer to add an SB to your household, what counts towards the expectation? The total cost of the household, $5K? Perhaps just the marginal cost, which is to say, how much extra you will be paying to add one person to the household, for arguments' sake, let say $500?
Either way, this is a very different number than writing a $5.5K a month check to a SB.
So to me the universe of what SDs have to offer and what SBs wish to have would contain an almost infinite number of combinations, since it's all very subjective.