The setting was pretty cruel and crafty, but not totally unreasonable. Megumi made a mistake by first going for hardier ingredients instead of cauliflower. I don't actually much care for cauliflower personally, so I don't know if it's so problematic in reality, but I guess it is. The setting was like a miniature version of the challenges a restaurant owner faces while procuring the various ingredients needed for the menu dishes. Some can be handled in a more relaxed manner and stay good for a long while, some might be harder to acquire and go bad fast. Different strategies are needed. So, it wasn't only about Shinomiya being a jerk (although he is a jerk through and through).