It's hard to math out exactly due to all the spices, (I'll use coriander, cumin, cardamom, mustard, ginger, garlic and garam masala in most curries) but the major cost drivers are the beans, tomatoes and onions. I'll use 3 medium onions for half a pound of beans and around 6 tomatoes/peppers. This'll make around ten to fifteen lunches, depending on your portion size (I usually bring rice and a veg with mine, but sometimes I don't have a roasted veggie ready). I haven't done the exact math since before the pandemic, but then I estimated it at $0.80 a meal, so it's probably closer to $1.40 now.

Edit: pricing is for the bean/lentil curry (masoor or chana dal are my typical go tos, but I'll usually throw in some urad dal and I've used fava beans with success). Chicken curries bring up the cost, but not significantly.