In 2008, Symbiote Studios produced a set of 1,000 signed polystone Sam & Max statues.
Recently, as spotted by Scummbuddy on the Mixnmojo forums, the original Steve Purcell concept drawings for the statue sold on eBay. The seller listed them for a cool $4,000, though they actually sold for an undisclosed "best offer" sum. I assume $3,999.99.
I'm unsure how these drawings ended up on eBay, or indeed if they've been seen online before, but you can admire them all below.