If someone is posting a tut for sale, I see no problem in posting a link to a free one (if it exists) in the same thread.
The reason being is this is not a secret society message board. Each tut should stand on their own merit. Plus, most members go on to offer the paid tut on their own website or etsy store.
Many times, free tuts don't offer enough information or supporting photos for those trying to learn a new procedure. They may look at the free tut and feel they need something more.. something that might be more explicit.
Paid tuts, by their very nature, usually offer carefully labeled step-by-step instructions along with email and/or video support.
Let each member decide what is best for them.
Again, just my