My first reaction is to guess that people now are "worth" more than people in 1600 because they have access to more productivity-enhancing equipment, including life-extending equipment. So a proper accounting would make it more like 6000 people. Furthermore, more productivity from someone in the year 1600 would facilitate exponentially more resources (including life-saving resource) over the time since, saving more than 6000 people. After all, that's why interest exists -- because the forgone opportunity grows exponentially! So, even valuing the people equally may justify sacrificing the 12 million for the one.

But I freely admit I may need to rethink that.

Also,

an AI with a 5% temporal discount rate has a nearly infinite incentive to expend all available resources on attempting time travel - maybe hunting for wormholes with a terminus in the past.

There is a financial argument against the possibility time travel that was published in a journal (don't have the citation offhand): if it were possible to time-travel, interest rates would be arbitraged to zero. Realizing this, wouldn't the AI give up on that goal? [/possibly naive]