I will never forget selling vehicles online in the 80's. After three years, I had my own advertising, my own customer base, my own phone pops, set my own hours, and got paid on everything. Although most of my inquiries began online or with a phone call, I had the highest gross average in the store.
Just like your inquiries, phone pops and emails would be about trying to get a price from me to shop. I never aloud that to happen.
I told them that I work by appointment, I told them the above, then I asked:
"So, let me ask you, you will phone-shop, then make an appointment with the biggest liar?"
They would balk, ask what that meant, etc..
"Let me explain the result of what you are doing: we all pay the same price for vehicles, exactly what they are worth, wholesale. We all need to make a little profit, not too much, but a little. If you don't like being lied to, you are not going to like this method of shopping, because the guy who tells the biggest lie gets the appointment.
When you show up all beat up and angry, he will just tell you "I lied", but often you will give in anyway."
Caught off-guard with this, they would ask, "what choice do I have", or vent because it made them angry.
Then I would ask:
'May I suggest and alternative?"
"How about I send you links to multiple places where you can do all of your research online, then you can know what I know, including the value of your trade-in, and what I pay for the vehicle. Simple, easy, takes only a minute. Then, you set an appointment with me, we both put our cards on the table, and we make a nice, straight, clean deal in one wack?"
You would be surprised how well this worked.
"I do not want to dicker with you, and, at the low price you are going to be willing to pay, I like to do it this way for obvious reasons. Is morning or afternoon better for you, and where shall I send these links?"
I sold over 2,300 vehicles in my 15 year career as an auto salesperson, and I had so much fun, that I would do it again for the right job.