That's $295 a piece for the S&S holders.

The best price on the Lisco/Fidelity holders before they stopped making them was around $375 each from Calumet. $1K/pair was the price for the Lisco/Fidelity holders with the non-breakable slides from B&H. I have regular slides in my 8x10" holders and haven't broken one yet. I've encountered broken slides on very old holders, but if the holder lasts 50-odd years before having to worry about the darkslide cracking, that's not a bad service life.

The other options are AWB and Lotus, which were both even more than that when I last checked.