I was being a tad cynical regarding the strudel - but it is overpriced, but you can hardly blame the Viennese for milking the tourists!
As you say, there's a lot more to Vienna than weekend breaks, but the clientele for river cruises are likely to look for somewhat higher quality travel options than Ryanair Group to get to their cruise ships. River cruising is very expensive. I'd say, especially with the (unpleasant) prospect of a fall in sterling were things to go badly wrong next Friday, there'd be a good inbound market, for shopping, if nothing else.