Also, possibly some exchanges don't charge for 2nd usage from same customer. My only issue with 15M delayed would be when I'm running a live and test strategy on the same instrument and get some value from seeing both acting on the same data. I can resolve that by just using two Sierra Chart's, one on sim, one live for now.
That becomes 2 (virtual) devices. I dont really see what the problem is.. either run sim and live on the same machine at the same time. Or if you really must run them of different machines then create a subaccount (+corresponding demo account) and pay for the second set of data yourself.
Millionaire, the problem arises if you are trying to use both sim and live accounts at the same time. I trade my live account and test automated strategies on the sim account. Currently you can't do that anymore because they don't let you run both at the same time, in particular they don't provide price quotes on both at the same time. It will slow me down greatly to not be able to test while I'm trading. So they are actually losing commissions, as I would be able to get a new account trading quicker if they allowed sim/live usage at the same time.
I trade Crude Oil futures using 5 minute charge. Buying the data for them outside of IB is very expensive. At least on my budget. The subaccount thing is interesting, but I have an individual account. Dunno if I can create subaccounts.
Since they store quote data in a database, they don't need to run a separate delay server. A request for delayed data only needs to lookup 15 minutes back in the database, instead of retrieving the most recent row. I was logged into both my live and my paper trading account on 2011-Apr-08, from the same PC.
Since you have to run both on 1 pc, just make sure you code perfectly every time and never lock up your pc with something like an infinite loop error....