Pacific Oil Cooler and Aircraft Spruce are two of the main vendors to buy SW coolers. Yes, they have gotten breathtakingly expensive over the past few years and that's a typical price for a two-pass SW8432R. I paid around $600 for a new SW10599R almost 3 years ago and Pacific Oil Cooler gave me the best price I could find.
A cheaper alternative, which is also a 2-pass cooler with physical dimensions almost exactly the same size, is the Aero Classic part# 8000343 for about $590. It's a "drawn cup" construction, more similar to the way that Niagara NDM coolers are made, than the welded-on end tank design of the SW coolers. An even cheaper alternative you might consider is the Aero Classic part# 8000081 which is a single-pass, 10-row drawn cup cooler that is only about $250 and will fit on the cyl #4 rear baffle on an RV-8 and should be able to adequately cool even a heat-monster engine like an ECI Titan IO-360 with piston oil squirters.
Aero Classic also makes their new "HE" line which look to be constructed much more like the SW coolers. They're considerably more expensive than their regular drawn-cup coolers, but cheaper than the equivalent name brand SW (now made by Meggitt Troy?) coolers. Spruce and Pacific websites both have cross ref info for these on their respective websites.
Whatever one you choose, I'd at least give Pacific Oil Coolers a call and see what they can offer. Back when I bought the SW10599R, they beat Spruce's price by nearly $50.