Healing potions are able to be created by independent people in small settlements.
Trying to compare us to them just isn't going to work.
I think they are much easier to get than you're giving credit for. I can live quite comfortably on $1500 use/mth. I make an average salary for my country and it is much higher than that. I could easily buy one in this scenario after 2 months of saving while living comfortably. Not a decade or a year.
Except for the majority of human history, most people didn't have incomes that massively exceeded their costs.
Instead, most people had direct access to food (because they where farmers), and little access to coin. They usually paid their taxes in a share of food. Savings where invested in having more food or animals and better food and kids who had better nutrition, not coins. They might have specialists, but they might pay the specialists in food, or in tally sticks, not coin.
The rich, people with liquid assets, whose survival expenses are far below their income, where extremely rare.
Not having enough food to not be hungry was common. Saving money instead of buying more food so you aren't hungry was a challenge, and often sub optimal, because food is energy and health. Scraping up enough savings to represent literally months of middle class living expenses is a bit crazy.
Take a world where there are 1% upper class, 5% middle class, 24% lower class, and 70% poor, where I define "poor" as "doesn't have enough money to avoid chronic undernourishment". The lower class has regular hunger, but it isn't
always.
Here, I'll define middle class is defined as people who can
usually afford the 1 gp/day standard of living.
In modern day, take someone living in relative poverty. How many of them can save up for a single purchase that represents about 2 months of a top-5% of population living expenses? Even if mathematically possible, such a purchase would be really extreme.
(There isn't a financial system to make buying that potion on an installment plan possible without usurious interest rates. Although, I expect that to happen; a local moneylender willing to take title to your farm animals and a 5 gp (or a donkey or equivalent animal) per month in exchange for an emergency healing potion.)