Thought I'd help my fellow brides who are up to envelopes (like me!). So FI and I are making our own invitations, but we decided to consider outsourcing envelope printing. I've done a ton of research locally (I live on Long Island) and also called places like envelopes.com and such with no luck - either they don't have the right color or they're super expensive.
But....today I found LCI paper (www.lcipaper.com) and they were a pleasure to speak to on the phone. You can go online and check out hundreds of colors in dozens of finishes and order samples of each for $1.25 with free shipping. For printing, they'll do front and back side for $1.25 each or a few cents more if you pick a metallic paper and that cost includes the envelope. I live on Long Island where prices are higher I think, but quotes I was getting as a comparison were anywhere from $2:00 - $3.25 each and in some cases that didn't even include the envelope itself.
Hope that helps some of you!