Breastfeed the first 2 but not the 3??

I’m really happy about breastfeeding my first two kids but my 2nd breastfed till she was 2 and would wake up multiple times a night to breastfeed and it took so much out of me. I wasn’t planning on having another baby but here we are and I just think it would be a lot better for my mental health to just formula feed. But I know it would be cheaper to just breastfeed ahhh I don’t know what to dooooo.