CVS:

First, I bought the Contour Meter.  It was on sale for $19.99, and I had a $10 coupon.  I used $10 in ECB's, paid nothing, and got back a $15 ECB.  Made $5 profit!

Then I thought I would end up making money on the next transaction, but I did my math W-R-O-N-G in my hurry to get out the door.  Not unusual for me, haha.  I ended up asking for all of my manufacturer's coupons back when I was checking out and just paying with $15 in ECBs...I didn't make a profit, lost a little, actually, but at least it was all free.