Usually when the budget is opaque there's a reason for it. Money really seems to be wasted for the most part, and the digital library has always been an embarrassment. Years later, it still has no API, and last I checked the terms of service forbid you from accessing it with software! Completely braindead. The only reason to join ACM besides accessing the crappy digital library is to save money on conference registra…
However... I'd probably be in favor of unbundling this and other commercial services from ACM memberships.