Using hosting costs as an index is nonsensical. I wasn't able to find numbers for 2009, but since 2015 the monthly page views have remained almost exactly constant. So you might as well claim that they're vastly overpaying for hosting since inflation from 2008 is way less than 3.75x.
Ultimately every person has to decide for themselves whether they think WMF is a worthy recipient for their donations, but it is in no way operating on a shoestring budget nor staffed by volunteers anymore.