If you are looking for an inexpensive alternative to shortbreads from the shops, "baking it yourself" might be an option. By making your own shortbreads, you end up with two advantages.
You can control your ingredients, which is especially relevant for allergy sufferers, and you can test out your own variations according to your taste preferences. No matter which type of flour you use, make sure that the flour is as fine as possible so that you achieve the typical consistency. You can find numerous shortbread recipes on the internet.