Yep Bicycle Blue Book FTW!
It's pretty helpful. Your LBS also may be helpful if you are a loyal customer and they don't do a lot of used volume. Mine does not, so trade ins with road bikes are hit and miss. They gave me a much better deal on my MTB because that's what they are most likely to sell quickly for a "better" price. Their comp was slightly higher than BBB but not by much.
And I agree that you have to be fairly patient but you can find them. It's just a chore haha. Some people look at it as an adventure (I do when I get a wild hair to search) but it's not always fun if you have a deadline. And, honestly, your bike does not make you that much faster. A good fit can but a carbon frame will only do so much. I was always taught by everyone I started really riding with that it was the motor and fit not the material and weight that was going to make a huge difference (assuming that most road bikes are fairly light, of course). If you want carbon, totally go for it, just realize that there may be other issues at play and if you don't know much about fit, CL bikes or ebay bikes may not be the best place to start. Getting fitted on your current mount may be better. YMMV.
***proud Hoosier, statistics nerd, and mom to a headstrong toddler***
****one car family and loving it!****
Owned by:
Le Monstre Vert - 2013 Surly Cross-check
Chessie, Scottish Terrier
Bonzai, Catahoula Leopard Dog