"I think she'd like the boss and maid option."
"Right, just wait right here." He walks down the aisles, mumbling to himself. "...and here we are!" you hear him say. Seconds later, he appears with a large box, and walks over to the counter. "If you could just come over here. Cash of card?"
"Cash," you open up your wallet and gives him the five hundred. "Wait, are these the right sizes? You never asked me about sizes."
"Yes, don't worry about that. In fact, if they don't fit, I'll go even better than the usual guarantee - you'll get $550 back for them, or $100 off another set of costumes. Sounds okay?"
If he's so certain about it, you guess you accept his word for it. You thank him for the costumes and leave for home.