Two men, one flat bed truck, 5 windmills in one day. Well maybe ignoring the generator. The key here is that the support for the central spindle is relatively simple - just a plate on the solid ground, with spikes banged through. The windmills/turbines are erected as a large marquee tent would be - guy ropes, pulleys, strong arms and hopefully no wind.
What differentiates this from standard horizontal axis windmills is the construction.
With horizontal axis wind turbines (HAWT) on hillsides, and the flat, you need a decent foundation (concrete), and potentially a concrete tower to support the weight of the generator with most likely has to be bought in by helicopter. That's costly by anyone's standards.
Don't even mention the the maintenance cost of the HAWT. With this design of VAWT, you could just lower it to the ground with the ropes/cables again. It weight perhaps 1000 times less that the HAWT.
The likelihood is that the VAWT with sail cloth will be less fatal to birds. Potentially less interfering with radio signals too. Both of those are 'in theory'.
Lastly, the HAWT design requires a support more than half the length of the blades to stop them biting the ground. The VAWT design, being guy-roped can go much higher in the same square-footage on the ground.
Next up pictures of the Meccano model from 1991 that actually worked. If I can find the negatives.