... you are trying to lay a foundation for deeper mathematical understanding, which a kid isn't going to pick up by memorizing math facts. They need to understand place value. .... That does not actually come as an automatic understanding to most kids. You need to explain it to them. So if you're good at those sorts of things, go for the cheap workbooks. If you're not, then use a scripted curriculum like Math Mammoth or Rightstart or Singapore.
This is excellent advice, though as someone who learned math "the Asian way" and understands it in those terms, I still appreciated the help I got from Singapore and Miquon in presenting those concepts such that my kids could gradually build and then deepen their mathematical understanding. (I don't think of Singapore as at all scripted. Though I'm not one to purchase or use teacher's manuals, so maybe that's why?)