> A very significant amount of people won't go back
So they didn't need what they were about to purchase and saved their money. Doesn't sound like a net loss to me.
> I don't think you understand how ecommerce works ... people won't go back
I was talking about the economy in general, not specific e-commerce sites. People that actually need what they were looking for but don't go back will buy it elsewhere. The money still flows, just somewhere else. And if they don't need the item(s), they'll perhaps use the money for something more useful.
A very significant amount of people won't go back. It's why the most effective marketing campaign by far is retargeting those people to convince them to come back. Unfortunately that's not possible in this case since you can't track the users as the site is unusable.