I built a Rube Goldberg machine in high school as part of Science Olympiad (http://soinc.org/).
It might be a surprise to some that the machine with the lowest budget one, but it's not to me. We also had essentially no budget--I think we spent about $5 on parts--but ended up placing 5th out of about 25 teams. And we had actually had a chance to test it before we went to the competition we would have done a lot better.
You can easily spend hundreds of dollars on these things (and some of the teams we competed against did), but it's not going to actually get you much. When you're building a machine that's complex by design, you really want the individual components to be as simple as possible.
It might be a surprise to some that the machine with the lowest budget one, but it's not to me. We also had essentially no budget--I think we spent about $5 on parts--but ended up placing 5th out of about 25 teams. And we had actually had a chance to test it before we went to the competition we would have done a lot better.
You can easily spend hundreds of dollars on these things (and some of the teams we competed against did), but it's not going to actually get you much. When you're building a machine that's complex by design, you really want the individual components to be as simple as possible.