As I mention downthread, the usual measure of damages in contract is expectancy - i.e. what value would party B recieved if party A had fufilled its part of the bargain.

In this case the bargain was akin to a undated bond (the UK issued some of these), in exchange for a payment up front and infinite stream of payments. The net present value of such is straightforward to calculate; one interesting property is that their nominal value is not dependent on the time since issuance, thought their real value drops with inflation.

The law is not unreasonable, it allows for efficient breach. No court is going to order specific performance (i.e. that Joyent actually carry out its promise) but it will have to make good via monetary damages.

US courts are sophisticated enough to understand such bargains (at least since Posner was appointed to the bench in 1981).