Ahem... a 7 minute ride from our hotel to the train station came up to 35 CHF. That's around 5 km, so around 7 CHF/km or 6.25 EUR/km. Just something to these dreamy 56 rappen and realism of the study in perspective.
If you look at the full context, I think the article states that this is the price which could be achieved by an optimally sized fleet of driverless taxis - it even says right there that the actual, current price with conventional taxis is much higher than that figure.
The current taxi fees in Zurich are actually even higher than 2.73, even before factoring in the base fee and fees for waiting times, but I don't see how that in itself would limit what prices driverless taxis can realistically achieve.
[1] https://www.stadt-zuerich.ch/content/dam/stzh/pd/Deutsch/Sta... [2] https://www.uber.com/de-CH/blog/zurich/preise-zurich/