IB is way cheaper than tradestation, as a matter of fact they are the cheapest non-professional (in my opinion) broker. Trading 1 lot will usually cost you around 2-3,5$. Only minus is that you have to pay for market data, but (most costly ICE~100USD) even with that it will be way cheaper than tradestation.
Also, you get 2USD worse price because they included commision in your execution price. So you payed 2usd commision.
Tradestation is not considered 1st choice as a brokerage by many. If you prefer the charting, yes.
Re ThinkOrSwim: Are you certain you can`t open an account with them? Normally they would not let you do trades on margin, only cash backed longs. But this would let you use all of their analytical tools.
Why not go first to free dough.com (founded by former TOS founders). They are introducing brokers to TOS (and this grants you a better rate at TOS). Open the TOS account through them.
I live in Australia and have the same problem - TOS, Dough are not available to me. I was told that non US citizens can not open a TD Ameritrade account, with the exception of Canadians and Singaporeans.
My solution to this problem is Option Vue 7. It is a bit messy, but workable.
As an alternative, I am planning to look into Hoadley Options software, a set of modular Excel-based software tools for the analysis of options, which connect to IB TWS.