After they get going, I don't see how the capex could possibly be higher than for a traditional tower wind turbine. Everything is smaller, and closer to the ground. Less site preparation, and you don't need to rent giant cranes. You're also not shipping giant blades and pylons with special trucks.
Also, using smaller generators means that you've got a higher production volume, which can mean significant cost savings. You're also not dealing with giant bearings, gearboxes, etc. which are expensive to produce.
And if you're taking a kite offline, you might as well replace all the motor-generators at the same time. I assume they'll be designed to easily detach and replace. Then, back at the shop, you can check them out on your test bench, and see which ones can return to service in the spares stock.
Also, using smaller generators means that you've got a higher production volume, which can mean significant cost savings. You're also not dealing with giant bearings, gearboxes, etc. which are expensive to produce.
And if you're taking a kite offline, you might as well replace all the motor-generators at the same time. I assume they'll be designed to easily detach and replace. Then, back at the shop, you can check them out on your test bench, and see which ones can return to service in the spares stock.
I agree that the tether is a big question mark.