That being said, my food costs were easily cut in half when I went vegan (and now, they are about 1/4 after some fine tuning of some other recipes) - I mostly get protein from chickpeas, kidney beans and lentils - which are all super-cheap compared to meat. I also eat a fair bit of tofu (which is very low in fibre and which is also very cheap compared to meat). Tempeh is another option, but I don't tend to make it often. We generally cook a big batch of food at the beginning of the week - which means time to prepare is amortized nicely (and frying tofu is very quick also)
I will admit that processed vegan meat-alternatives do tend to be more expensive than their animal derived counterparts, and not the healthiest - so I tend to avoid them - most of the expense is due to small production runs and limited quantity - and the extra processing.