When the gym appraiser puts a low blue book value on a gym business it is based on real current values that have sold. It has nothing to do with a percentage of the new selling price.
The low blue book value is what a used fitness equipment broker will pay for it. Haul it back to his business facility to be refurbished and resold to the next user.
This is about the same as a trade-in at the car dealership. The real value is added after the fitness equipment is moved, inventoried, refurbished and repaired like new. And then marketed and advertised to find the next retail buyer.
This is the value a bank wants to see when a Gym owner is not making payments and will get shut down. This is also the value a gym operator wants to see when he is buying brand new gym equipment and wants a trade-in value.