You could take a leaf from the real middle ages, where soldiers and other retainers very rarely if ever got *paid*! They got food, shelter, weapons, clothing from their lord, who obtained those from other retainers or as tax from vassals. In 4e it's quite easy to say that the mundane economy is largely non-monetary - maybe measure it in 'bushels of wheat' or something else other than gold, or just handwave as necessary.
Real gold can be used to hire trained mercenary companies, Italian City State style, but those guys will be *darn* expensive because they operate on the 'adventurer economy'. Your regular retainers and levies don't get paid gold, though; numbers are limited by other factors including personal loyalty, population base, the amount of wheat in your graineries, etc.
Stop thinking like (post) industrial age people, think barbarian-turned-feudal, and it gets a lot simpler.