Here's the slightly amusing story to go along with it. I was only going to do $2k to get started, and just have more cash in my checking account for "unexpected" expenses. But when opening the account, the Vanguard rep told me "The minimum for VTSMX is $3k". So I said "OK, lets do $3k". Bam! DONE. Prior to MMM I'd have been all like "Oh, well I need to wait for my next paycheck, just in case." But now I know I can easily make it to my next paycheck even after going in for an extra $1k.
Ah, the beautiful combined power of having a budget and increased frugality.