Not Going Postal, But Still Annoyed

This weekend, I had to send out some very important paperwork that had to do with part of my employment. It came in one of those big manila envelopes, so I figured I'd send it out in something similar, so as not to get everything all folded up.

Now, is it me, or didn't mailing something that was that size, but still lightweight (the mailing in question weighed 1.3 ounces), used to cost the same as a regular letter? I was pretty sure that was the case, but I decided to put it on the self-service electronic scale at the post office just to make sure it wasn't overweight. So I was more than a little surprised to discover that the machine expected a dollar's worth of postage instead of the 42-cent "Forever Stamp" that I had already affixed to the envelope.

Obviously, I'm not the only one who was under the impression that the cost was the same, as one of the options offered to me was to make up the difference between the regular stamp and the dollar. I did this, and it printed me a new label, so hopefully the presence of the label and the stamp won't confuse the person who handles it. And then, since the machine can't accept charges of less than a dollar, it printed me a 42-cent computer-generated stamp for later. It wasn't an arduous process, but it still really took me by surprise.

So does anyone know when the price went up to mail the larger envelope? Did it coincide with the most recent rate hike? Or had it been more expensive all along, and I had somehow just gotten away with it for a long time? (I'm really doubting the latter.) Chime in via the comments if you know.