https://zero-k.info/mediawiki/index.php?title=Economy_GuideThis could use re-wording and updating.
Edit: buildpower is in the ui. single unit has a bar indicating buildpower in use, a group of units has buildpower in a number next to HP values, metal values, burst damage income etc.
Edit 2: Think every second that all the builders stand in a bread line. Metal income gets added to storage. Builders ask for their buildpower value from the metal storage. When they get their metal they spend it, and return to the end of the line for the next second's metal. If you are going even or have storage, everyone gets their metal every second. If you are empty and a glutton of buildpower, they each get the same PERCENTAGE value of their buildpower every second.
High priority gets a premium line that goes before the normal line(they get to cut). Low priority has another line that only gets metal when normal has gone(they let everyone pass them). A reserve limit will act as 'empty storage' for everyone except high priority.
When you have metal above the reserve limit, everyone gets served. When you have metal below the reserve limit, only high priority gets served. If the buildpower of normal and high priority gets fufiled by income and metal is at/above reserve, low priority gets served.