They are not (directly) competing with restaurants, but with supermarkets. They have clear benefits above supermarkets, as they do not have to throw away food. They directly send it to their customers. Furthermore, their food prices are a lot higher than buying it yourself in a supermarket.

HelloFresh buys in bulk, so spices/nuts etc. are especially packed for one box. Which becomes really inexpensive if you serve the same kind of food world wide. This massive globalization is (or will be) their competitive advantage.