You are refering to 150000 as text and I guess it should be a number. Remove the " " (highlighted in red) and it works.
Code:
Wrong
IIf([contracttype]="GS" And [Award Amt]<[COLOR=red][B]"[/B][/COLOR]150000[B][COLOR=red]"[/COLOR][/B],"No eval")
Right
IIf([contracttype]="GS" And [Award Amt]<150000,"No eval")