I would say you have a good keword with the advertisingforum the .biz does hurt some... without any traffic or revenue i would guess mid to high XX ...
with your KU9.biz being that you can still get pretty decent 3 character .nets at reg fee and you can get decent 3 character .coms around $50-100 i would say not much more over your reg fee on the .biz.... this may change in a couple of years if all 3 character .nets and .orgs get reg.. but for now unless you can optimize it I would say low XX
just my 2cents worth