<p>Sustainable and healthy diets are crucial for reducing diet-related diseases, safeguarding planetary health, and promoting equity in food systems. This study calculated the minimum cost of omnivorous and vegetarian diets, based on the new Austrian food-based dietary guidelines, compared to the actual Austrian diet based on the Austrian Nutrition Report 2017. Food price data from 13 retail outlets covering 220 food items were used. Using the least expensive 3–7 products per group and recommended intake levels, we calculated diet minimum costs and assessed affordability relative to income and food expenditure data from Statistik Austria 2021. The estimated minimum cost for the actual diet was 6.74 €/day (organic) versus 3.81 €/day (conventional). The omnivorous diet cost 6.27 € (organic) and 3.37 € (conventional), while the vegetarian diet was cheapest at 4.62 € (organic) and 2.83 € (conventional). On average, organic food items were 75% more expensive than conventional equivalents. Expanding food diversity increased costs by 9–10% per additional item per food group. For organic products, the cooperative supermarket was least costly. For organic omnivorous and actual diets, minimum costs were above the food expenditures of the lowest expenditure decile, while for organic vegetarian diets, they were below this threshold. The lowest income group would need to spend 12.7–19.5% of their income for an organic, and 8.0–8.6% for a conventional, minimum-cost omnivorous diet. Minimum-cost approaches may underestimate the lived reality of food poverty and access barriers. Policy actions are needed to support affordability, accessibility, availability, and social inclusion to ensure that sustainable and healthy diets are attainable for all segments of society.</p>