It can be used as a tool for designing a budget cube, but that wasn't the original intent. I think the approach to this data was for people to say "I have $20, how can I best spend it to upgrade the cube?" So instead of buying one $20 card, you can buy 10-15 staples for the same cost. This was a good place for players to find a list of affordable cards that will stick around in their cube for awhile.
These cards aren't just cheap, they've beaten out some tough competition to earn slots in many of the tightest cube lists in the cube community, so I'm happy to recommend them as good value that should be efficient, powerful, and/or versatile enough to be worth a slot in your cube for years to come.
Also you if you are looking to find alternatives at a specific cost you could try Cube Tutors search function like this for example to see what creatures people are running at 6+ mana in white.