A lot of work on software development is done by the paid staff. And Wikipedia - and also accompanying projects like Commons, Wikidata, Wiktionary, Wikisource,

A lot of work on software development is done by the paid staff. And Wikipedia - and also accompanying projects like Commons, Wikidata, Wiktionary, Wikisource, etc. - are complex pieces of software with long list of features requested by users. Even if it weren't so, running site of this magnitude requires an operations team that can not be volunteer. So, pretending that the hosting bill is the only (or the main) expense that goes into running Wikipedia is silly.