I got a bill in the mail today with a weird envelope. The flap (opening) of the envelope is on the bottom; i.e., if you look at the front of the envelope right-side up and then flip it to the back, the flap is not on the top as you’d expect, it’s on the bottom. And printed on the flap it says “Cost-saving bottom flap envelope.” What in heck does that mean? How does it save costs, and whose costs are being saved? All it means to me is that I have to flip it around to open it at the flap.
This says they work better in envelope inserting machines …
Reverse flap envelopes have mail inserted from the bottom rather than the top. The orientation of the address window is typically on the left side of the envelope. Bottom flap envelopes, due to the design and orientation, flow and run much better in envelope inserting machines.
Bottom Flap Reverse Window | Envelopes Only
That’s interesting. It’s weird that they print “Cost-saving bottom flap envelope” on the flap. It’s hard to imaging why they do that.
I suppose it’s to signal people that the envelope was intentionally printed that way, and that the orientation of the address field was not some kind of mistake.
Or perhaps it’s a psychological trick. If the mail that this envelope comes with is some kind of advertising that the sender wants you to respond to, then printing this enigmatic phrase on the envelope makes you wonder and inquire further (as you did). So you’ve given this thing more attention, which increases your likelihood of responding.
Or, they printed a bunch of envelopes upside down by mistake, and rather than throw them out, they then printed “Cost-saving bottom flap envelope” to make people think it was done on purpose. 
Interestingly, if you also put the bill in upside down, the printing stays in place better. They don’t have to buy the more costly extra sticky ink.
Or they could just put the whole stack of paper in the printer upside down and print all the bills upside down, which should have the same effect.
I first noticed this phenomenon 40-some years ago, at which time I worked for a very large company (actually, a government research lab). I noticed that our paychecks came in envelopes like this. When I asked about, this was the answer I got.
Yeah, like ‘this page intentionally blank’
Yep. I suspect that printing this on the outside of the flap stops quite a few phone calls they would have to field from people who felt it necessary to tell them that they made a mistake on the bill. Of course, if the only mistake is the flap is upside down, it’s not significant, but it would take a human talking to the caller to determine that is what the problem was. With those words on the flap, the call is never made.
Fewer jams, less downtime, less manual labor = cost savings