It found that in high-income countries:

• Vegan diets were the most affordable and reduced food costs by up to one third.

• Vegetarian diets were a close second.

• Flexitarian diets with low amounts of meat and dairy reduced costs by 14%.

• By contrast, pescatarian diets increased costs by up to 2%.

https://www.ox.ac.uk/news/2021-11-11-sustainable-eating-cheaper-and-healthier-oxford-study

Compared to meat eaters, results show that “true” vegetarians do indeed report lower food expenditures

https://www.sciencedirect.com/science/article/abs/pii/S0921800915301488?via%3Dihub ---(looking at the US)

Based on primary data (n = 1040) collected through an online survey, representative of the Portuguese population, through logistic regressions, it was possible to conclude that plant-based consumers, particularly vegan, are associated with lower food expenditures compared to omnivorous consumers. In fact, plant-based consumers are shown to spend less than all other consumers assessed

https://agrifoodecon.springeropen.com/articles/10.1186/s40100-022-00224-9