As @xzap042 pointed out, Xeons are generally 'much' cheaper than their 'iSeries' equivalents. There are two reasons:
- Xeons CPUs generally lack an iGPU i.e integrated graphics so a discrete GPU is a must, otherwise you won't have any display.
- Not all boards support Xeons so the demand is lower + a lot of people don't even know about their existence!
For example, I was extremely careful when I bought my H81 motherboard as an awful lot of H81s simply don't support Xeons. Of course you can request a hacked BIOS from the users at www.bios-mods.com forum but there are always some risks and caveats that go along with them and there's always a slight chance of bricking your motherboard for good!
P.S Xeon E3-1220v3 prices have gone up considerably in the past week (4.5k > 6.5k) but they're still a lot cheaper than regular 4th Gen. i5s (~12k).
Sounds like a loophole to me! Worth a shot, I'd say.