MR has had especially good comments lately:
The problem with this thought experiment is that even if every
individual (or all but one) have an upward-sloping individual demand
curve, the market demand curve will still be downward-sloping. The
reason is, when people who seek higher prices will run out of money
faster, thus buying fewer units. So higher prices still lead to fewer
units sold — i.e., a downward-sloping market demand curve.
Or how about this:
Your curve slopes upward until it reaches the point where quantity
times price equals your wealth. From there on, it slopes down (you buy
as much as you can afford, which is less and less at higher prices).
So everyone would quickly spend all their money.
Oddly, some goods might end up with demand curves that slope down in
the relevant price range– in spite of the buyers’ preferences!
Perhaps you’ve already spoken your mind, but comments are open again, in case you would like to take another crack at the problem. And remember, spent funds are recycled to sellers and do not represent the destruction of real resources.