I have very simple tax return (kolel check, wife on W2, daycare, mortgage interest). Will an accountant save me enough to justify the cost, as opposed to using TT. Thanks for any advice.
He may be able to give you advice that will save you money in the future, that you didn't think of, so its probably a good idea to use an accountant at least once (or once every handful of years). For example (1) he might say If you put X dollars in an IRA, your income will be lower and you will be eligible for certain valuable tax credits or (2) he may recommend unique opportunity for matching contributions to 529 plan for someone with low income, in certain states.
It would be nice if you could hire an accountant to just review your return and provide relevant advice, but most accountants won't do that, or charge you at least as much as it costs to complete a simple return.
Similarly, even if you do primarily use an accountant, doing it yourself first on TT once every handful of years, will help you get educated, and probably means you'll get more out of working with an accountant, and how to be more efficient about taxes (e.g. long-term vs short term capital gains etc).
Another benefit of having an accountant, is if the IRS decides to audit, you have a professional on your team generally committed to helping you, even though he will probably charge for that. Navigating that alone can be very stressful and is often not a good idea. Finding a professional to jump in to help you at that point is much harder and more expensive.