If I think they're MORE than a tire-kicker or referred by one of my good clients, my line is something like...
I charge by the complexity of your return, which is more than I can see from your documents. It requires me to ask you lots of questions; and you can ask me lots of questions, too. I need to review your prior year returns to prepare this year's anyway, so if you loan me last year's returns now, I'll be glad to tell you how much I would've charged for THAT year. Then, you can compare apples to apples. However, with the Tax Cuts & Jobs Act and the SECURE Act plus any changes in your financial life since 2018, your 2019 return fee could be very different from 2018. Not to mention the new CARES Act which changes our planning for 2020. When would you like to drop off last year's return?
If there's an entity return or a Schedule C/E/F or even a K-1, the above "talk" gets more detailed.
I still give a price RANGE and try to quote a high enough top range to give myself a margin for error and to make the new client happy when I come in under my estimate, telling him something like..."because you were so organized which saved me time and saved you money...."
I'm way off once in a while. I've usually stuck to my high point on the range with a warning that I am reviewing my price structure for next year. I have called a client in the midst of preparation to say I've found something you didn't tell me about (maybe one of the 92-page gas & oil K-1s) which changes your fee to $XXX; would you like me to continue?
If they come as a recommendation of a very long-time client -- one that I've raised prices slowly over the years -- and have a similar return to their friend's return, I find myself torn. A stranger walking in the door would get a much higher price for a similar return than a very long-time client. But, the friends have talked with one another. I pick a range higher than their friend/my current client but lower than what I'd charge a complete stranger. Then, I'm back to the "reviewing my price structure for next year" warning. I've lost only one of those, and that was years ago.