The world is not binary. Between 0 Tax and 100% Tax is a lot. National economy is something completely different than business economy. The main difference is the tax cycle in national economy. A simplified example: If the city of Vienna spends 1 Euro in buying trams, this Euro goes to the company Siemens in Vienna building those. Siemens employs a Viennese worker getting this money. 42 Cent of this invested Euro comes back to the city as tax. And a small part of the new tram. And a better public transport because of this new tram. And a new company settling in Vienna because of it's superior transport system. And another part of the 1 EUR comes back again as tax of this new company. If clever done this cycle does not stop.

Asking for ROI of Vienna's infrastructure investments is as absurd as asking how much tax did a business get back from his investments.