Yes, but that valuation is intrinsically linked to the potential sponsorship deals that the current owners are able to achieve through their business connections. Many corporations want to do business with companies attached to sovereign wealth funds. The mutual benefits are obvious.
For instance, lets say a Greek shipping family bought the club. Would Sheikh Mohamed bin Zayed Al Nahyan hand them a 400 million pound sponsorship deal? Absolutely not. They would have to start from scratch with Aegean Airlines etc..
I understand that this is a hypothetical conversation, but in any scenario where the club could be sold, as soon as you remove the current ownership from any future involvement, the price would be significantly lower. And if you don't believe that the house of Nahyan can squander money, since 2016, Etihad Airways have written off 7.8bn in losses.
In comparison, there is a lot more to show for their 2.1bn investment in City, which is why I cannot see them ever selling up. Businessmen like to attach themselves to success and winning. Khaldoon has even listed City's honours in his list of
achievements on his Wiki page, so there is a huge level of pride attached to this unique relationship, but the exploits of Etihad Airways looms large on the future of this club.