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Factoring in Time Value of Money & then working your way to a fair & reasonable seems to be the way to go.
For example, lets say you invested $2,000 USD b/w 1964-1974 & another $3,000 1974-1984 on RS LP's, 45's etc. How much would that same $ be equivalent to today? (that's the real value of $ invested).
Also your buyer(s) would have to spend a lot of time & $ chasing down the rare/semi-rare stuff, so factor that in (& use it as a selling point, i.e. convenience to them, saving time & $). Also they get to see the merchandise & possibly sample it etc (known quality & quantity/value/safe investment)...another selling point. Also, they save on shipping, which adds up quickly per LP. Also your collection is damage free vs. something they ordered online, which may not be (hassle, refund status questionable)...Peace of Mind.
Even a collection of "basic" mainstream LP's, the examples above apply, just on a slightly smaller scale of varying monetary degrees.
I'd prepare a nice spreadsheet/word doc w/descriptions & pics (the sizzle) to entice the buyer(s), let them scroll/flip through it, now it's tangible, if they're not physically holding the records. This imprints on their mind & adds to their desire for your collection.
Don't accept the 1st offer (if possible), unless it's way, way over what you were hoping to get initially. Just don't sell yourself short.
Lastly, put your best LP's at the front & back of the stack, with a few scattered throughout the middle. Humans tend to remember the 1st & last thing they saw.
I hope this helps you get what your collection is truly worth & wish you the best of luck!