I definitely think they will lose more money from people who are perma-banned than from people leaving in a tissy fit over a game. Yes without a doubt.
Personally I have spent thousands on this game over the last 4 years, as has my husband who has been playing for 7. If we got banned, we would move on to Neverwinter or use it as an excuse to get a life. We stick around because of the new quests and raids and as we have high level characters we want to be at the top.
If Turbine told us that you were taking away his completionist and 15 other characters all with at least 4 lives on them and then all of mine that are similarly leveled (minus the completionist) to have to start from scratch Id say they were crazy and why would they push us into another game.
DDO has to compete with many other games right now and they need everyone they can get. These exploiters are the same people that pay big money to see things continue. They are in part why Turbine continues to make quests and expansions.
I'm sure Turbine will sit down and say "ok XXXX people took part in this exploit. If we perma ban them ... How much would we lose? ... how about for one month? ... or 2 weeks? ... or one week?" They are a business and as upset as everyone is, try and look at it as a business. You better believe Turbine will. They will have their analysts working on it to weigh out the risks and then pick the least risk to them.
In no way is the least risk a perma ban. You don't want to be turning away paying customers... what kind of business would they be? Not a very smart one , that's for sure.