I was expecting it to go $6-7K
Well lets compare the two based purely on numbers,
fathersday.com.au searches for term 9900, cpc $4.66
happyfathersday.com.au searches for term 320, cpc $0.10
fathersday.com.au: 9900 * $4.66 * x = $4101 domain value
therefore x = 0.0888
happyfathersday.com.au: 320 x $0.10 * 0.08888 = $2.75 domain value
.
That's always a good way to compare on metrics. However your domain doies have a brandable element to it's value too (which is always hard to put a figure on of course)
Probably a keeper but not that much more I don't think