If the molding won't stay on despite being correctly inserted in the slots, you may need to replace the Molding Retainer (the part with the slots). It's only $15 from Ford.
As to pricing, if I order from Tasca they sell the trim for $62.06 plus $21.17 shipping. Total $83.23 plus tax. Shipped from Rhode Island to me usually takes a week and a half.
If I order from parts.ford.com and pick up at my local dealer it's $82.38 plus tax. Available the next day after ordering. In addition if I sign in when I order it gives me FordPass points as well.