Putting a price on any lp or cd is open to many things. How quickly do you want to move it, who is your buying base, does grading play a big part to your attempt to sell it. All of these questions need to be asked before pricing.
When I sell at the local record collector's convention I need to realize that condition is everything. Most of the folks there already have at least one copy and are looking for a mint copy to replace it. I also know that a properly priced classical or jazz lp probably won't find many buyers at a local show.
Unless it is a truly rare and difficult to find piece, you are competing with other dealers who only want to make double what they paid for the item and they are then happy. It takes patience to get the real value out of a good lp or cd.
Some folks seem to rely too much on price guides which usually are quoting prices that might be paid by two or three rich collectors on one of the coasts. One needs to take price guide prices with a grain of salt. There are only a few really "mint" recordings out there; everything else is somewhat less than that.
Personally, I use the guides to alert me to really rare and unique pieces..not common issues to be found everywhere. There are always exceptions to this rule but very, very few.
Closed Ebay auction information is probably the best measure of what an lp or cd is worth and you must know the grading norms intimately in order to judge correctly. I hope this info helps!!