Wow!
What a spectacular pair of speakers

They even have the CDWGs on the tweeters

In all cases the value of such speakers is based on what someone will pay. Brian is probably your best source of knowledge of what they cost originally and what performance they are capable of now, but ultimately it will come down to finding the right buyer who appreciates their heritage and updated performance.
IF you were to look in the market at comparable speakers of that size and performance, (google Montana, Dunleavy, and Legacy) you will find that they are selling for thousands.
I can't imagine upgrading them like you have and not KEEPING them
