Sisterlocks are not free, hell they are not even cheap. But are they worth it? Absolutely! You have to assign the value you think it's worth.
I suggest you utilize a certified Sisterlock consultant from the Sisterlocks.com website.
The first expense is the installation. I live in a major city. Installs here typically range between $500-$1000. It may be cheaper in smaller cities.
The second expense is retightenings. $20 -$40 per hour based on your location. Trainees typically charge around the lower end of the scale.
You will be saving on time, effort, styling tools, products, and potentially less stress surrounding what to do with your hair.