@Argolok - you're confusing him with a certain guy with a smartphone. Satou can't target spells through the map, and he doesn't have AoE spells that don't wreck the whole map.
@Kaarme @werewolf914 - Satou is a merchant. Paying is the merchant way.
If Muno family were doing well as rulers, they or their trusted retainers (like consul Nina) could have requisitioned the supplies on promises of paying later. If Muno family were doing really well, the populace would have volunteered supplies. But the barondom is in very bad shape, so I don't expect people to give their stuff without hard cash. At least, without creating a lot of resentment. And the current Muno family are really nice people, they would not do it.
But Satou isn't well-known in town, so he has to spend gold if he wants stuff done.
@Jorelm @Kayriel - yeah, the MC is selfish. That is realistic. Not everybody wants to be a superhero or a god and shoulder the whole world's weight on his shoulders. Especially not the overworked Japanese salarymen.
Maybe it'll be a lesson for you, to appreciate more heroic protagonists more. I see too many disparaging comments about main characters being heroic.