I did Row by Row last year. All the patterns are free. Kits where I went were in the $8-$15 range but for the most part I didn't buy kits. Some had die cut appliques which I couldn't replicate so if I liked that then I bought the kit but otherwise I just got the pattern.
I did try to purchase something at the shop because the purpose of Row by Row, other than to have fun, is to support the quilt shops by driving traffic to them. They weren't large purchases usually because I went to so many shops.
One downside of purchasing kits is you end up with no continuity of color from the different shops where if you use your own fabric you can achieve that to a larger degree.