My diet is a lot more expensive now than it was before - I ate lots of stretcher meals with my family (rice/pasta/beans in the main course to make it cheaper and go farther) and cheap frozen fare. Now, I eat mostly whole and unprocessed foods - lots of fresh veggies, dairy, meat, and a few specialty items like seaweed/pork rinds/stevia/etc. Our food budget has definitely gotten more expensive with my choices, but it's what it takes for me to be healthy AND sane
Two things that have gotten cheaper - my health insurance and clothes! Plus sized clothing, especially maternity, is SO pricy and the selection is very limited. Now I can shop much more easily and thriftily, with many more brands available for me to wear. I also have much better luck at thrift stores in this size range, whereas I didn't even try before!
And the health insurance - I went from expensive and almost uninsurable when morbidly obese to getting the normal rate or even cost discounts now, because of my changed BMI and clean medical history. That was a real, several hundred dollar a year savings to my family's bottom line, since we self insure.