I've had a "shared hosting" setup on Dreamhost for at least 15 years, also using pennies per month in capacity, at most.
I get that it can be a brutal, low-margin business, but I also wonder how many "small" customers are extremely high-margin like me, and whether that can aggregate into a better overall margin than you might guess?
Or will you always have a few outliers running at capacity and calling the help desk and blowing out your margins?