What's the best way to share Mac Apps downloaded via Mac App Store? We have four guys in the house running on Mac and say, one updates the apps that the others have purchased with their individual apple ids, could the apps be shared over a storage media/airdrop without app store pointing out for id issues?

Multiple folks downloading at the same time gets the bandwidth cropped and with the fair usage policy in place, after we hit the cap for the month the internet speed drops to a bare minimum. Well, apps like Xcode/Keynote/iPhoto which are fairly huge as a sum of all downloading the same copy.

I'm probably looking at something like steam backups, where I just share the backup of the game that friends have purchased but haven't downloaded yet and for them, it's just a matter of restoring from the backup file, without a problem, as they've purchased the game too.
If you are running Yosemite, then you can enable Family Sharing so that others can download the same app purchased by you.