Even without a sale, you can buy 5000TP for $50, or 100TP for $1. Can you earn more than $1 working that same hour at a job?
If so then by sitting in front of your computer running the same boring 11 quests over and over on characters you don't intend to keep, you are not earnigng TP for "free," you are technically losing money.
My buddy rebuilds cars for a hobby. I play online games. If I can keep from spending money at my HOBBY I'm ten's of thousands of dollars ahead of my buddy. If your goal is to make money get a second job and stop playing anything. Figure if you can find two full time jobs with a small commute you can spend about 100 hours a week towards making money. If you keep a tight control of you expenses and live in your car you should be able to make enough money to buy everyone in DDO a 500 turbine point card each Christmas.
Okay snark and sarcasm off. A lot of new players can gain a lot of experience learning how to build a character by doing the 100 favor dash. A lot of experienced players can get enjoyment by having a goal to make the "fastest" favor runner. Speed chess vs that long thoughtful version. My point is this is a game that can be rewarding for people who make goals for themselves. Be it actually finishing completing a slayer area or doing all the quests in alphabetical order.