Great question! Prior to last year, I used to go to the salon for a relaxer every 10-12 weeks (approximately 5 visits per year), which would cost me about $90. I also put in senegalese twists over the winter last year which I believe cost $140 including the hair. So, I have saved roughly $590.
However, I still process my hair with chemicals (texlaxing), and spent about $80 for the supplies to do it myself. I also decided against twists/braids for this winter and instead bought some wigs to use as a protective style, for $140. I've still saved several hundred dollars, but it doesn't feel like it.