I don't know if they've come down in price, since I usually don't keep my receipts until just a couple of years ago* because I never plan to sell my Volvos -- I just keep them until they're so old (~300K miles) that no one would want to buy them (mainly because of rust, in this part of the country), and then I just junk them.
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* until I got a scanner, that is, and then I just scan in everything and throw the paper away :-).
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Anyway, just FYI, the Cat's costs that's printed on my receipt is $266.19 (my price) and $295.77 (list price), for p/n 8551608-6).

But what threw me was the price of the 02 sensor -- $215.96/$239.95 (p/n 3501753-2)! That I didn't expect, based on the last time I bought a sensor, but for my '84. But that's a single wire type, and my '93 has heater wires also, so maybe that difference may account for the spectacularly higher price.