- Command Centre / Nexus / Hatchery
- Refinery / Assimilator / Extractor
- Supply Depot / Pylon / Overlord
- SCV / Probe / Drone
- Unit producing structures (or in the case of Zerg, buildings which enable the spawning of units from larvae)
- Structures where upgrades can be purchased (e.g. Engineering Bay, Forge, Evolution Chamber)
- Upgrades (e.g. attack upgrades, building armour upgrades)
My testing found that morphing buildings (e.g. Orbital Command, Planetary Fortress, Lair, Hive, Greater Spire) isn't counted at all, nor is the process of morphing units (e.g. Overseer). It also seems as if the construction of some buildings (e.g. Infestation Pit) isn't counted either, so it would appear as if the Spending Tab is somewhat buggy.