What was the most expensive record that you ever bought ?

Thorens 125th Anniversary LP. I paid $350 for a mint copy.

However, I sold an LP for $2k once. 

I have not bought an LP since 1982, and I don't remember what they cost back then, but I know that I wasn't going out of my way to buy quality pressings.

However, within the last few years, I did pay a seller $100 for a JVC XRCD red book of Linda Ronstadt's Greatest Hits .  (It was Different Drum that I really wanted.)  The seller was raving about the sonic quality, but I didn't think it was that great.  IMO, the DCC red book of Linda Ronstadt's Greatest Hits Volume 2 sounds way better as does the MFSL red book of Simple Dreams, and I could probably go on and on about CDs I paid a lot less for that sound a lot better.

Anyway, a while back ago I was taking it out of its jewel case and it snapped in half.

MFSL BEATLES BOX SET.

Original high-grade VeeJay copy of "Introducing the Beatles".  Don't remember what I paid, bc I eventually got a full refund.  The idiot who sold it to me mailed it 3000 miles packaged between two pieces of corrugated cardboard.  Worse, he'd cut those pieces from a cardboard box and positioned the box's crease right in the middle of the cover (LP inside the cover, of course).  As you've probably guessed, the pkg bent in the middle during shipping and the album arrived in two pieces.  And the guy didn't buy insurance. 

The worst part, though, is that the seller guy refused to give me a refund, and it took weeks of haggling with eBay to force the guy to give me my dough back.  eBay is not Amazon when it comes to buyer protection.

Echoing another poster, the two albums I SOLD for the most were a Second State Butcher Block and an original mono UK Trak copy of "Are You Experienced" (bought when I was a kid in 1967 off the shelf from a record store in Bermuda -- and played only a few times b/c, frankly the sound was awful to the point of being nearly unlistenable).  Both went for $5-600, which most people would find jaw-dropping, but here, makes me a piker.

earlier I wrote about the most expensive " Record " that I purchased 

but since the MFSL Beatles box set was just mentioned I have to say 

I Bid $201 dollars on e-Bay for a 1979 Japanese release of the Beatles Collection never thinking I would win but I did so $200 is the most I've spent on a " box set "

These pressing were better that the individual earlier Japanese pressing I have .