Actually, you can homeschool just about free, of course that assumes you go to the library for everything you need book-wise. I highly recommend using local libraries. There is also a website called Ambleside online which has free curriculum and a scope and sequence. In addition there is also the Core Knowledge curriculum that is not overly costly.
I use Core Knowledge to supplement, but not as our main curriculum. The things we do are more alongs the guidelines of the Well Trained Mind. The things we do use are relatively cheap compared to what is out there. I picked our curriculum purposefully to be the most cost effective over the longest amount of time, with the best quality material. Nothing we have requires us to purchase the next level, year after year.
The homeschool market is big business. It can be expensive because there are people are willing to spend a lot of money. However, it does not have to be expensive at all. The biggest investment is time.
When I was in the Navy, an Air Force friend of mine, a single mother, homeschooled her 6 year old daughter (the daughter is brilliant, BTW). I have no idea how she did it, but if she can homeschool on a E-5 income, as a single parent, then I think just about anyone can do it.
That's my problem. Single parent. So it would be really tough to do.
"Actually, you can homeschool just about free"
Time is money, and that includes today's American woman, sadly. We have taxes to pay.