I manage a small computer network with a couple dozen XP clients and a Windows 2003 server. The server has a large amount of storage and there are a lot of changes and additions every day. My somewhat paranoid backup system uses a total of nine hard drives which keep the data safe, but makes upgrades quite expensive and labor intensive.
When we were running out of space, I did some digging and found that one of the big space hogs was a legacy image management application that was used only for historical reference and static as far as file changes went. This old-fashioned program and data was neatly self-contained and would happily run straight off a network share. I could have moved this folder to an XP machine, except that the limit of max 9 concurrent connections would be a problem. Adding another Windows 2003 server and access licenses would add up to about $1300 just in software cost.
Fortunately, the Linux backup servers had enough extra space to hold this data. Moved everything over to one, mirrored it on another, shared it via samba, and we were in business. Probably bought us over a year's time before an upgrade is forced. Total cost: $0. Now that's real savings.