Adverb
in a ruinous manner or to a ruinous degree
Source: WordNetNothing's more exciting than a day in a studio with a string section - or more ruinously expensive. So it's good to feed that habit away from the band, especially if it means more experience for the next Radiohead string day. Jonny Greenwood
He was finding it ruinously expensive to be rich. Robert A. Heinlein
ruinously high wages Source: Internet