GoldenChest, I am doing something similar to you. Trying to collect every small size note type from 1928 to 1963 with exceptions of course (No high denom. notes, Just one set of 1929 nationals from NY, FRNs from NY or Chicago, No crazy rare notes such as '33 $10 SC). Getting star notes whenever I can afford it.
It is not an easy task sometimes but very satisfying when your nearing completion. I think if you can get older notes at FV your just using common sense because the older notes to collectors always have a premium, sometimes a small amount and sometimes a much substantial amount such as finding a national like you did.
I can't believe someone would spend a national honestly, It is very obvious its different, old, and most likely worth something more than FV even to those who know nothing about collecting US paper money.
I think if you decide to do signatures as well, you just complicated your task tenfold. Personally I avoid signatures and most differences within a series.
Hawaii sets are a more pricey set to complete especially in higher grades. I currently have a $1 Hawaii in UNC, $5 in EF, $10 in VF and $20 in EF. Right now looking to upgrade my $10 Hawaii. Star notes for hawaii notes command astronomical prices so I decided to avoid those.