I've had two even better (non-)MS in the last two weeks.
1) Bought something for $3.99 at whole foods (with the OBC getting 5% off). Realized I had bought the wrong flavor, and returned it. They gave me $4 dollars back in cash. Score! Just needs a bit of work to scale up.
2) Bought the wrong type of thing at CVS, returned and they said if the right thing was the same price just exchange rather than go through the hassle. Original purchase $6.79, correct product was $6.99. They said that's fine. So thinking should I exchange for something that's $7.19 and so on, till maybe get a $500 OV for $6.79? But too busy returning stuff at Whole Foods....