It's not "wrong", you're just parsing it differently. The title means that the poor don't enjoy any additional benefits from that growth, since their expenses scale accordingly; thus theie net growth in disposable income is "nothing at all".
There is a very good reason the title used quotation marks, and it's not because it's a quote.
"The poorest two deciles in bigger cities make about the same income as their counterparts in smaller cities"
Which does match the title.
I think there are a few obvious problems with this. But as a paper it's a good start. I object to the strongly worded title, but it's not wrong from the paper.