expensive

be, look, prove, seem, sound

That restaurant proved expensive when we ordered three courses and wine.

become, get

Houses in our city have become very expensive over the last ten years.

make sth

Hiring a professional designer will make your website more expensive than doing it yourself.

find sth

Most students find their textbooks extremely expensive when they start university.

amazingly, astronomically, enormously, exceedingly, extortionately, extremely, frighteningly, hideously, highly, horrendously, horribly, hugely, immensely, incredibly, inordinately, ludicrously, massively, outrageously, ridiculously, ruinously

Flying to Japan during holiday season turned out to be ridiculously expensive for our family.

impossibly, prohibitively

Private school fees are impossibly expensive for most families in our neighborhood.

increasingly

a bit, comparatively, fairly, moderately, pretty, quite, rather, relatively

correspondingly

Good quality shoes cost more, and replacement parts are correspondingly expensive.

needlessly, unduly, unnecessarily

notoriously

obviously

discreetly

She wore discreetly expensive jewelry that only other wealthy people seemed to notice.