Because it's Xeons which is a different line.
EDIT: read the children posts. I mistakenly read "chip" instead of "line". Of course Xeons are a different line compared to Intels extreme line. The above about the extreme series CPU's being cut down Xeons is still true but in this context wrong and irrelevant.
They bin things for a reason. If you're happy using a less expensive part with fewer features, great, you can save money. If you're making a top-tier "Pro" product you'll want to avoid cutting corners like that.
Also see my edit of my original post where I mistakenly misread "line" as "chip" as stated.
> They bin things for a reason.
Yes, of course, so that the extreme series doesn't cut into the margins of the server market. If you could run RAID 5 and 10 without hardware dongles and ECC on the extreme series some smaller companies would probably prefer the i9 18 core for 2000$ to the 3000-4000$ 18 core Xeons. Again, this is fine, but Xeons and extreme series start of as the same chip. That's all I wanted to say on top of my correction of my original post.
The materials involved are only one factor.