The best sub $50 saddle that I've found (and better than most $90+ saddles) is the rido. I really like it. I like it better than the brooks that I used for several years and much better than the avocet air that it replaced.

The rido costs around $35 with shipping to the U.S. depending on the price of the dollar. It's lighter than the brooks but heavier that the avocet (titanium rails), however, I can use my legs more efficiently to spin and it is way more comfortable.

Is it the best saddle out there? I don't know. I've found a saddle that works great and I have no desire to spend $150 on a Fizik Arione to see if it is better.