A Boeing 929 Jetfoil with ~450km range, ~300 passengers, 2x Rolls-Royce Allison turboshafts is often quoted to be ~$60M. Tickets are $35-$120. Many routes operating it has been seeking government subsidization to build replacements as hulls near ends of life; so far, only one 929-117 has been built since the turn of the century.

IOW, not a lucrative business on its own, makes _some_ sense as a subsidized public transportation.