The E-Mac (looks like a toilet, sounds like a jet) came with 256 MB of RAM in one of the two slots, adding a 512MB stick was dirt cheap (everyone had at the very least 1GB on their PC), well it was dirt cheap except if you bought it from Apple...
It's how Apple monetizes their customers. Figuring out an artificial shortcoming they can sell as an upgrade to them (check out dongles for example).