OP!! Personally I don't think that's a very nice thing of your SIL to say at all. Unless you made it clear that you wanted her financial advice (or were clearly falling apart with two kids) I'd hope family members would be supportive.....
At the risk of repeating what others said, some thing are cheap and some are not. Breastmilk is free but um, they do start needing other foods at some point!! Where we live, organic is EXPENSIVE and we pay a price for the healthy life we want to give ds. But since I can see how processed foods, preservatives, etc. affect him, I think it's worth it. I see the non-organic rght next to theorganic and I know how much I could save flat out
Also, homeschooling isn't free if you take into consideration the financial loss of the homeschooling parent's income. I don't think we can homeschool b/c while I can SAHM now, we will need my income later. I've heard people talk about saving money on school versus play clothes, but ds will only have one wardrobe :LOL
We also have good medical insurance which I pay a hefty premium for. Ds had surgery a few months ago and the bills, even after insurance, were really high. If he was on Medicaid the bills would have been less but he would have had to have the procedure done at a BAD hopsital with a non-specialist, which was not a choice I was going to make if I had an alternative.