About a decade ago, we realized that our books were more numerous than the library that Jefferson sold to replace the LC. Think of that: our late-90s collection - assembled by an ordinary couple in an ordinary suburban house - was numerically as big as the LC used to be, early in the 19th century. That's some sort of index of how rich our society is today.
Over on LibraryThing, they're loading in the catalog of TJ's library, the collection he sold to Congress to rebuild the LC after the British burned it.
"On Jan. 30, 1815, Congress approved the purchase of Thomas Jefferson's personal library of 6,487 books for $23,950."
So that's an average price of $3.69 in 1815.
(As it happens, that was a high point for American prices - prices had jumped by fully a third due to the War of 1812, and, except for the Civil War, prices would generally decline for the rest of the 19th century.)
$23,950 in 1815 was worth $323,830.99 in 2006: $49.89 per book
(A further 3% inflation gives us $333,546 in 2007: $51.42 per book.)
So, say, roughly $50 per book, mostly leather-bound hardcovers.
So, Jefferson's collection was sold for more like "Folio Society" prices than like "bookstore" prices.
(Sidebar: Note that relentless inflation is mostly a post-WWII phenomenon - American prices were essentially the same in 1941 as they were in 1815:
According to this calculator:
$13,075.32 in the year 1900 has the same "purchase power" as $23,950 in the year 1815.
$15,645.41 in the year 1915 has the same "purchase power" as $23,950 in the year 1815.
$24,190.95 in the year 1918 has the same "purchase power" as $23,950 in the year 1815.
$23,660.87 in the year 1941 has the same "purchase power" as $23,950 in the year 1815.)