I do tile so no substrate expenses, Once a month I do an order for a hornworm cup for about $15. Roaches and silks I breed. Veggies we grow, certain months out of the year I spend a few dollars on greens.
Conclusion: $15 dollars sometimes like $20
Every 6 months or so I buy new uvb bulb as well
2 eating machines who love BSFL and medium (20-25 each) crickets to large crickets (16 each) + an occasional superworms + greens (choys)
2 adult eatern bluetongues who love their salad, hard boiled eggs, and are treated to food grade live snails occasion and are fed soft doggy pellets 2 to 3 times a week.
1 eastern water skink who loves mealworms (worms & pupae), BSFL, and medium crickets.
I buy my BSFL and crickets online 2x p/mnth, mealworms in bulk every 2 months and supers in bulk 3x/ year.
Not breeding silkworm at moment ( will restart in spring )
I also feed the resident wild geckos, skinks, dragons and frogs, and insectonivorous birds, in warm season ( all yr other than May-Aug)
So > $100 incl shipping per mnth is about average for me.