Quote from Rodney King:
Huh? What's a historical dbase worth, a few thousand dollars?
Most charting software licenses are way cheaper... CQG comes to mind as "expensive" charting... but then it's expensive in part exactly because it comes with data.
Naturally, if you are prepared to buy data and charting platform separately (from the broker account and each other), the question of advantages of Tradestation is mute. There are cheaper brokers, better charting, better backtesting platforms and better data. They just don't come in one inexpensive package and don't work as seemlessly together.
Another issue is most providers of "live" datafeed don't offer long enough history of tick data. So, one ends up with 2 separare data sources: one for long history and one for recent history and live data. It is a lot of work to set up tick filters etc so that indicators and trading systems produce sufficiently close results on these different sets of data.
IB is not a good example of perfect datafeed. However, just to give an idea of what can happen when you don't have history form live datafeed... Normally IB data is filtered. However, this summer IB had a spike in prices of a number of futures. It affected even hourly bars in IB backfill. Such a spike hadn't appeared for a good number of months before. Without a history of "bad" dat one can't properly build a filter to take care of it.
Further, historical data would typically require conversion before it can be used by a charting/backtesting platform. Maintaining up-to-date history on all symbols of interest becomes a separate project etc...
Note, all of this vast amount of work and money adds nothing to your bottom line. It's just required to get started with what Tradestation does out of the box.