Threat of substitutes

Sir, in the May17 MCS variant 3 there is a question about the threat of substitutes. It is about a pound shop style business and the suggested answer keeps on saying how there is a threat of substitutes as the products are generic and there are virtually identical products available on the market for similar prices. Now, the thing is that I always thought substitutes were products that serve the same need but in a different way. So for a $1 can of baked bean another $1.05 can of baked bean of a different brand is not a substitute but a competitor. A substitute for canned food would be a meal out in a restaurant, maybe. What do you think?