Someone asked about pricing. Here's a link to the Russell web site.
Custom Motorcycle Seats and Touring Saddles - "Day-Long" Touring Saddles and Motorcycle Seats by Russell Cycle Products
Prices range from around $600 to maybe as much as $900, depending on choices you make for materials, suspension, heat, etc...
A used Russell seat in very good condition usually runs from 70% to 85% of the new price, depending on the season. Russell gets stacked up during riding season, so anxious folks will give more for an already built seat if they think it will fit them.
Here's a link to Corbin's web site.
Corbin Motorcycle Seats & Accessories | Triumph Motorcycles | 800-538-7035
Corbin seats usually run from about $450 to $650 depending on options.
A used Corbin is priced similary to a used Russell, i.e., in very good condition, you'll probably pay 70+% of the original price.
Corbin builds their seats on their own seat pans. Russell seats are built on your original non-modified stock seat pan.
You can ride in to Russell and they'll build your seat on the same day. I think Corbin offers the same service.
Russell has an excellent reputation for service after the sale. They are anxious to work with you to provide the comfort you desire. Corbin has a reputation for expecting the customer to live with the product, or to resell it if it doesn't work for them.