That's pretty spot on. I thought it was going to be a useless rant. Whenever I'm selling stuff on CL, that's pretty much what I set as my "minimum" price. I'll take those numbers, add ~20% for the bartering factor, and then list it.
For example, I've got a 75g on CL right now, comes with a diy stand. Asking $125, I'd happily accept $100, probably even $90. But people barter, so if I listed it at $90, somebody would want to pay $50...ain't gonna happen. I'd rather keep the tank.
However, where the author differentiates the "year or under" aquariums, I disagree. Used is used, and you can't take someones word for how old it is. Whenever someone says "Yeah, only 6 months old" that means at least 18 months. Used is used. $1 per gallon for tanks.
I had a 2213 on there complete with media, asking $60(which I got...woot, would have been happy with $45). Anyway, I also have a 2128, asking $150(would accept $120). Some lady called yesterday, confused the two, and thought I was selling the 2128 for $60...and then offered me $40. I politely declined.