I try to pay as little as practical, it differs with the different cartridges. Been handloading most of my ammo for the past 40 years, I generally buy components, not loaded ammo.
What you pay for ammo is only significant as a percentage of your income. I can recall paying $.09 for a round of rifle ammo that today sells for $1. But back then gas was $.60 per gallon of premuim, and I earned $300 a month.
All else being equal (and it almost never is) bigger bullets tend to work better.