The Permanent Wealth Evaluator is bought ingame, Not in Solomon's Store.
-Click on the Wealth Evaluator icon in your Inventory interface (the picture of the abacus shown between the Currency Pouch and the Price Checker).
-Once you click on Buy Now, choose the option Buy - not Rent. The price shows 240 Runecoins, which is 50% off, so it is cheaper to use Runecoins, instead of Bonds. (Redeem 2 bonds for Runecoins before purchasing it.)