Eight fluid ounces of Huberd’s Neatsfoot Oil can be purchased for as little as $8.99 on Amazon. I have been using it on my Brooks B17 for two years. It keeps the saddle leather supple and somewhat water resistant.
One of the best features of the product is that it does not leave a residue that will come off on your riding clothes. I usually use it after a ride so that it has a chance to penetrate before my next ride. Even though I apply it generously, I have never had a stain on my clothes.
If you happen to check out the topic on the Internet you will find as I did that opinions vary all over the place on treatment of leather bicycle and horse saddles. There are some magical formulas that people use. The problem is that it is difficult to prove hypotheses about the goodness of these potions because there are no long term study results published.
For what it’s worth, I use Huberd’s and I’m happy with the stuff.