There are both national and local electrical codes that need to be met. Personally, I would always have each machine on its own circuit for safety and maintenance reasons. Yes, the more copper and disconnects and circuit breakers you buy, the more expensive it gets. But, what is expensive is liability when someone gets hurt. Also be wary of wires sizes, I have found that what is usually recommended in charts and tables is one wire size smaller than what is needed to avoid voltage drops.