The Macedonians had access to plenty of natural resources and weren't afraid to use them. The bonus allows them to have the storehouse technologies researched instantly after investing the resources. I've honestly no clue how good this bonus really is, as I'd assume that players will put higher priority on getting the upgrades due to them starting to pay back immediately.
I initially applied the bonus by adding -1.00 research time for it to be completely instant but instead of showing 0s research time it didn't show any at all and the time display got wonky if you had the 'gift from the gods' enabled. So I opted to just multiply by 0.01 as it's effectively the same thing but doesn't present any of those issues.