Your calculation looks correct to me. (WolframAlpha confirms “10^52 * 1% * 1 billionth * 1 billionth * 1%” is 10^30.) It seems that Nick Bostrom is underestimating the expected value by 10^10.
A minor factor of ten billion 😉
A mere order of magnitude of an order of of magnitude!
Thanks for your reply. I’m glad my calculation doesn’t seem way off. Still feel like it’s too obvious a mistake for it not to have been caught, if it indeed were a mistake...