I used to be a huge PJ back when I first started learning out how to deal with my curls, but I think I slowed down on that especially lately. I just seem to have less cash around to spend on new products, and honestly I have plenty of HGs. So anyways:
Suave naturals coconut cowash (lasts a month) - $2
GVP matrix biolage conditioning balm (lasts 2 months) - $6 on sale
kinky curly knot today (lasts 4 months) - $12
curl keeper (lasts 4 months) - $24 (with shipping)
Aussie instant freeze gel (lasts 2 months) - $7
Devacut every 6 months - $60
I think that comes to about $30 per month. That's just my basic regimen without DTs or other treatments added in. I don't think curly hair is very expensive if you stick to a bare bones regimen; and you can definitely do all drugstore. I think straightening treatments or expensive flat irons can come out to around the same amount of money, even if you're using less products. But it's far less time to go curly.