This is my first spin swap. However, the swaps are about the same. No dollar amount was mentioned, it is up to the giver. 90yds is what is obligated. That's it. It is all up to the giver.
A survey was sent to everyone. It had you list any allergies, hobbies, and skill level.
My suggestion is to do a dollar amount. Do a few ranges such as $15, $25, and $35. Something like that. If it is a spin swap, yardage is something to consider.