As they scale up, the costs will be lower. It's a supply chain thing, not a fundamental limitation. The input costs are lower. In the broader sense, plant-based diets from whole-foods are actually already cheaper
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
This is also true in real spending data
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
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=ihub (looking at the US)
EDIT: I should also note that in an increasing list of countries, non-whole plant-based things like this are already cheaper too. With meat prices rising further, that's only likely to increase more