Final answer:
High rent costs is the major cost disadvantage independent of scale for a retail business dependent on drive-in customers.
Step-by-step explanation:
In the case of a retail business dependent on drive-in customers, the major cost disadvantage independent of scale is High rent costs. Rent is a fixed cost for a retail space, meaning it does not change regardless of the amount of production or sales. This can be a significant burden for a retail business, especially if they are located in a high-demand area with expensive rental prices.