I have not looked for a good source of cheap indigo yet, but the henna I buy is excellent.
I get 1 kg bags for $8 (1000 grams!) from an Indian grocery store. That's $2 per application on quite long hair.
I will bet you can find indigo somewhere else. I know that Lush sells a henna indigo combination to achieve brown results.
I would guess that if you used it and left it on for just a short time it could give you lighter brown/dark blonde results.
$63 sounds like a lot of money for a product that is actually very inexpensive.