Unless it's a highly curated collection, filled with sort after titles starting at the $100+ price point, I can tell you that you're going to be laughed out of the record store if you tell them you want 60% of the median value.
'how long is a piece of string'?
You'll have to put a weekend aside and go through the collection doing some research to get an idea on the value., Youre looking at anywhere from $0 to $1000 for the mass circulated, average condition, land fill type of collection to $100k+ for a collection of mint first pressings and the like of popular genres.
