AMD and Intel can afford to spend a large amounts of money on design because x64 chips are sold at high margins in high volume. If you are interested in the economics of the chip business, [0] is a great Usenet post by John Mashey[1].

[0] https://groups.google.com/forum/message/raw?msg=comp.arch/9T...

[1] https://en.wikipedia.org/wiki/John_Mashey

Edited to remove a duplicate footnote.