This is something that I've wondered about going back to even earlier Civ versions. (And for all I know, it works differently in BE.) Why just ONE? As the FIRST of its kind, I can easily see why the significant bonus it provides. But (using Civ terms) Just because someone else got there first building the Pyramids, NOT having _any_ Pyramids of my own deprives me of the benefit it provides. I can also see that as a Johnny-come-lately, my 2nd set of Pyramids won't seem nearly as impressive. So whatever a Wonder's benefits, scale down that benefit until benefits hit a minimum baseline. Sort of like the Transcontinental Railroad. BOTH the CP and UP were winners, even though UP (1032) laid more track than CP (742). Since they were "paid" with with land grants per mile they built, the overall "winner" had more to show for it.