This definitely falls in the cheap category. You're using software that they provide and designing an end-around to avoid paying for it.
It's an interesting question whether this behavior is ethical. I'm not so sure that the proposed use of TurboTax's software is an end-run around paying for the services being sold. TurboTax makes its software freely available for the public's use and charges only at the point when a user decides to print or e-file the return(s). The
terms of service for TurboTax's online product state that:
"You are only granted the right to use the Services and only for the purposes described by Intuit. Intuit reserves all other rights in the Services. Until termination of this Agreement and as long as you meet any applicable payment obligations and comply with this Agreement, Intuit grants to you a personal, limited, nonexclusive, nontransferable right and license to use the Services."
And I don't see anything in the rest of the terms of service that would indicate that you are not permitted to use the software in the proposed manner.
When you pay for TurboTax's online product, you're not just paying for the use of the software to calculate the figures for your tax return (and if that were the intention, then presumably TurboTax would put the software behind a paywall instead of the current configuration where you aren't required to pay until the printing/filing stage); part of what you're paying for is the convenience of having TurboTax prepare your printed/e-filed return for you, store your information for future purposes after filing, etc.
Do you think it would be unethical for someone to prepare their own return by hand but then use TurboTax to calculate their tax liability in order to double-check their work (which, I believe, is a common practice)?
Again, it's an interesting question, and I'm not sure where I come out. But I don't think the answer is quite as cut-and-dried as you suggested.