Closest I could get was from Respectfully Quoted: A Dictionary of Quotations (Suzy Platt, 1993), pg. 229, which checked the attribution. She stated Jefferson couldn’t have said it because these words weren’t in use during his era:

“Inflation was listed in the Oxford English Dictionary in 1864, but the OED gives 1920 as the earliest use of the word “deflation”.”

From there I double checked 19th and early 20th century Google books, and it looks like what she wrote is correct.

But if not Jefferson, then who? The question still stands.