Total ingredient cost for a $3 loaf is about $0.75. Adding in cracked grains or seeds brings it to c. $1.50 for a $5-6 loaf. Total ingredient cost for a $20 pizza is about $3. This is for a "good" pizza. A Pizza Hut-grade pizza is probably $1.50-$2.00 in ingredients and sells for $9-10.

Now: bakeries do not sell every loaf of bread they bake. Quite a bit of bread goes stale, gets made into breadcrumbs, thrown out, sold at discount, donated to food pantries.

Pizza has much less spoilage because of the process: most ingredients, including the dough, are refrigerated. The dough needs 48h (could be as short as 24h) to ferment, but then stays good in the fridge for days. As long as you have a big enough fridge, the inventory problem is pretty simple to manage. Cured meats (sausage, pepperoni) have a long shelf life with refrigeration, as does cheese. Vegetables also last for days. The end result is that (albeit with some added costs from refrigeration) you're able to make the products on-demand as the orders come in. With bread, the product must be prepared well in advance and there's more waste.

A well-run pizzeria is pretty lean on labor, too. Plenty of pizzerias get by profitably with one or two men in the kitchen and one man at the counter.

But if you don't believe me, believe the market: most bread is produced industrially, sealed in plastic, and shipped to retailers on trucks. Small profitable pizzerias are ubiquitous.