A continental Breakfast is generally included in most hotels/B&B.
Italians are not big breakfast eaters. A typical breakfast is a cappuccino and a croissant, which you can find for under 3-4€ at any coffee bar, if you don’t sit down at the table (if you sit down prices are higher in tourist areas).
Lunch and dinner at a regular sit down restaurant have the same prices, unlike in the US where menu prices are lower at lunch. In my experience eating in Italy (which is vast as my size can attest) on average I spend approx 30-35€ per person in Florence, Venice has similar (high) prices. But I don’t go to fancy restaurants, those are prices for an average restaurant. That is inclusive of primo, secondo, contorno (side dish) and at least one half liter carafe of house wine, which I share with my wife, and maybe one dessert (share with wife). Fish will cost you more. Pizza less.
If instead of going to a regular sit down restaurant, you plan to have lunches on the go, or at an equivalent of a taco truck (for example inside the Florence Mercato di San Lorenzo), you can spend less than 10-15€ for plenty food.
Food in Italy is generally cheaper than in America, certainly cheaper than in the SF Bay Area and Portland OR as well (have relatives up in PDX, so I’m familiar with restaurant prices there). I can’t get away with just $40 pp around here, certainly not if I order even just a glass of wine.