This processor was this price a month ago. Now it's back. That's the lowest a quick search showed (to make sure I wasn't reposting).
Note: last time some price matched with Staples for less than $250.
You can also bundle with certain motherboards for $30 off the total (found on the product page).
Yes, current gen processors are better. But there are probably a lot of people who spent a couple pennies for a z170 or z270 motherboard with an i5 or i3 chip to upgrade later and want to get this proc at a good price before they become scarce and hard to get a good price on. That's who this deal is for.
Hope this helps!