Nordex-Germany building 120 m concrete wind tower in Brazil.
Do wind towers need to be built from steel? Not necessarily, concrete will work as well (or even wood) or a mixture of concrete and steel. A lot depends on the local circumstances and availability of materials. In many cases concrete will be easier to acquire than steel, which requires mining and processing in blast furnaces, where concrete is made of universally much more locally available cement and sand. The price of concrete is about $200-300/m3. The price of steel is ca. $5000/m3. Density concrete 2.5 tonnes/m3, steel 8.0 tonnes/m3 (not that you can draw direct conclusions from these figures).
The advantage of having taller wind turbines is the exposure to higher average wind speeds, which consequently require a more constant wind profile over the height of the rotor and larger blades. The race for harnessing the most power from wind energy is bringing some manufacturers to a path of alternative materials like concrete… There are already several wind farms around the world using this alternative in Chile, Denmark, and there are upcoming new projects in Spain and the UK.