A recent report written for the UK government[1] estimates that the per megawatt of energy could get down to 62.50 USD, assuming that the system would run for 100 years--according to Sabine Hossenfelder[2] this would make it cheaper than Nuclear and more expensive than ground based Solar.

[1] https://www.fnc.co.uk/discover-frazer-nash/news/frazer-nash-... https://news.ycombinator.com/item?id=36177739

[2] https://www.youtube.com/watch?v=3ZPrIE5ZMZA https://news.ycombinator.com/item?id=36177739