Think about what some of these toons are worth just in terms of work and time. Sure not every moment playing your account is dedicated to improving its actual monetary value, but if you look at it from an economical standpoint, think about how much of YOUR time has been put into this.
Now, I'm not saying this is what these accounts or characters are worth, just putting some numbers out there. Let's say you have 60 days played on one of your twinks. If you worked 60 days at a minumum wage job in the U.S., you would make
(60 days)x(24 hours)=1440 hours
(1440 hours)x(7.25$ -minimum wage US)=10,440$
So, if you value your time to be worth that of a minimum wage job, the amount of work you put into your twink would be 10,440$, disregarding sentimental value. Clearly this account or character would only be worth that to the original owner, but it's just something to think about. You can either be depressed or intrigued by it, just thought it made for an interesting point.