I'm looking at it as something's on the floor mispriced, you buy it, you leave... Like I said, retailers even honor that... They eat that kind of mistake.
If you buy something, go back to return it then with the intent to "take advantage", it's just different to me. I think retailers would look at that as significantly different too. It's an extra step or more.
For the Scout Speeders, at least for me, it was just me wanting 3 and they were mispriced so I just bought them... My last one was full price, but I still bought it. I have it yet, and could try this "trick" to get basically a Rep Shuttle for $17 (and one less Scout Speeder in my collection), but it is those extra steps of going back, buying the shuttle, returning the scout in its place... Not sure any of these stores are giving the store credit (I thought that wasn't tested, just the "swap" thing).