The average CEO makes about the same amount of money as the average dentist. When you get to the big scary numbers, you're talking about the top 100 highest-paid CEOs, not CEOs in general. Out of about a quarter-million CEOS around the country, a very very few of them are managing companies the size of Walmart and it's not at all obvious (at least, not to me) that those few are being overpaid.
> there are dozens of people who can make those decisions, and many could do so for far less.
Sure, or you could make the decisions by having a monkey throw darts at a newspaper for free. The important question is whether those dozens of people earning less would make as good decisions as the one currently doing the job. If the current CEO's decisions are even very slightly better he's worth the money given that level of scale.
Similarly, there are dozens of people who could play basketball for less so there was no need to pay Michael Jordan the big bucks.