I don't draw the same conclusion with lower values with L5 as they use rubber on all drivers. Lots of people see foam rot and lower pricing due to "blown woofers" or a xperienced buyer can chisel seller down on pricing do to the cost of repair and such. Also these days most people see L3&L5 as large speakers and L7 just obscene in size. I can appreciate you trying to keep values down here to further your L series hoard. But both buyers & sellers should just look to eBay for tmv as that is a true indicator of the marketplace. I bought L65 with car subs installed for 100.00 and sourced correct woofers for 200.00 so does that mean market value is 300.00??? I don't think so.
Well, I'm certainly not the flipper that you are, so far be it from me to be impartial in my evaluations!

And do a subject search for repairing those rubber surrounds, particularly on the L3, if you want a reason NOT to buy something!
It really makes no difference what we say here. It's a tempest in a tea-pot. The market will determine value for any vintage JBL. If you simply price the individual components of an L7 by what they bring on Ebay, no one would ever attempt to sell one intact ever again . . . if profit was the motivation. The LE120H-1 by itself usually brings for a pair on Ebay more than what I've paid for a complete pair of L7s. And that's not including shipping. Ebay is far from a barometer of what large speakers can be had for locally, and it is woefully unfair in results of large speakers with no cache in Japan, but it's pretty much the only barometer we have with any repeatability. If you check out completed Ebay sales for L7, you'll find two pairs that did not sell at asking prices of $1000 or more. But there's a pair of empty, water-damaged L7 cabinets that did sell for $350, with networks. Wonder where the drivers went??
As for L7 versus L5 pricing using Ebay as our basis in "fact", there are two pair of L5s no-sale completed auctions at asking prices of $535 and $700 with either local pickup or $200 additional shipping. If you go by Ebay asking prices, the L80T is nearly worth more and I have two pair of those (one bought for $50 plus some surrounds and the other for $100 with new replacement woofers from JBL). Both were found on Craig's List. I've even done the T3 crossover retrofit and they don't hold a candle to the L5, much less the L7. Ebay prices may be the only barometer we have . . . but as such, it's fairly useless. Use your ears, instead!
I've never sold a pair of speakers, though I've given away several in my over 60-year JBL experience. To the contrary I buy almost every JBL that looks like a deal in a model I want to try (including two pair of LSR305s). I may occasionally pass them to friends to enhance their audio experience, or display them all in a working situation for comparison—or drag some to the homes of others, similarly afflicted, for comparison. But selling off the collection will be up to my heirs to handle.