Low Athlon 64 quantities make motherboards scarce
This article over at The Inquirer suggests that yield problems are preventing AMD from flooding the market with Athlon 64 processors. Since only one relatively expensive speed grade of the 754-pin Athlon 64 is currently available, weak demand may also be a viable explanation for a lack of processors in the channel.
Whatever the cause, the relatively low number of Athlon 64s on the market appears to be discouraging motherboard manufacturers from releasing Athlon 64 boards in quantity. Pricewatch isn't exactly overflowing with listings for Athlon 64 boards, which may remain scarce until AMD unleashes more significant Athlon 64 quantities.