one is that two Eliezers would presumably be better than one, though I don't have a strong intuition about the optimum number of Eliezers.
The cost of keeping a carbon-based Eliezer alive would mean that whoever pays the bill would have less money to run the uploaded Eliezer. So the uploaded Eliezer would live for fewer years. Since it would probably be cheaper to run uploaded Eliezer for a subjective year than to keep carbon Eliezer alive for a year, running only the uploaded Eliezer would mean more Eliezer years overall.
The cost of keeping a carbon-based Eliezer alive is negative so long as his productivity exceeds the cost of giving him food to eat and a place to sleep. The existence of uploaded Eliezers may drive up the price of resources (or drive down the price of Elizezer-thought) until that condition becomes false, but that's not going to happen with the first copy. Thanks to comparative advantage it may not happen for a long time afterward either; the resources humans use and the resources computers use aren't perfectly exchangable.
In this video, long about 48:00, Eliezer talks about uploading and about how it wouldn't be murder if his meat body were anesthetized before the upload and killed without regaining consciousness.
It's arguable that it wouldn't be murder, but I'm not clear about why Eliezer would want to do it that way. I've got some guesses about why one might want to not let the meat body wake up (legal and practical complications of a double but diverging identity, the meat version feeling hopelessly envious), but I'm not sure whether either of them apply.
On the other hand, I can think of a couple of reasons for *not* eliminating the meat version-- one is that two Eliezers would presumably be better than one, though I don't have a strong intuition about the optimum number of Eliezers. The other, which I consider to be more salient, is that the meat version is a backup in case the upload isn't as good as hoped.
More generally, what would folks here consider to be good enough evidence that uploading was worth doing?