I own two EPI vintage loudspeakers. What drives the value down is that you need a very specific buyer for your Epicure 3s and it's a very small pool of them. Furthermore, depending upon where you're located, since practically speaking you can't ship them, the buyer pool could be miniscule. Whoever will buy your speaker is someone who really likes vintage EPI/Epicure loudspeakers. The idea that you could get some random person to pay $300+ for a pair of 40 year old, modified loudspeaker just because they sound pretty okay is a fantasy upon your part. You need to find an EPI collector. It is possible that you could get $300 for them, but it might take you a year to do it.
Try the AudioKarma website.
Good luck and please post what happens.
Try the AudioKarma website.
Good luck and please post what happens.