Yup, bearing in mind it doesn't even come with a display, 400 pounds for that system is a rip-off.
For nearly half that price you can buy a better system for brand new:
dabs.com - Acer Power FH Pentium Dual Core 925 1GB 250GB DVDRW Windows Vista Home Premium (PS.PFHC3.U01)
Your system is worth 150 pounds at the very most I'd say.