It seems to me prices are rising more than inflation should dictate. I think it’s because of the way profit is calculated. Am I wrong?

So when I worked retail and had to deal with pricing items for sale, there was a formula used that came out to multiplying the cost by 130% to get the sell price. An item that cost $3 would sell for $3.90 and there is $.90 profit. But take that same item and increase the cost by $1.00. Using the formula, sell price becomes $5.20, not $4.90, making it a $.30 increase in profit to the seller. Businesses are not only recouping the increase in cost but they're taking profit on it as well. Am I missing something?

edit: Replaced “They're not only” with “Businesses are not only”