harley96, you are braver than I.
Tell her you can sell the RA100 for $145 and you just trippled the quality of your reference chain for a mere $150.  Actually she should despise you if you failed to take advantage of this shining opportunity.  Besides, by doing extra chores/projects around the house you can pay for the purchase in a couple of months!
Wear you motorcycle helmet when you tell her.  Maybe the humor will soften the blow--so to speak.