Looks like a decent set of 50 year old Ludwig's to me!
I start at the top. What is a perfect condition kit like this worth? $1500 or so? Now, start deducting from there. Rust present? New heads? Condition issue's? Non original hardware? Extra holes? Everything is a deduction. Then, base your offer on that.
I've walked away from many deals because the seller looked at too many fleabay adds or saw perfect examples on line, and that's the price they were sticking to. They won't budge on the price usually, so I walk!
On the flip side, if they are reasonable, and you can point out some things the kit needs, you can make an amicable deal!
Good luck, and remember, condition is EVERYTHING!