I not see telling price over phone is issue. Some people on tight budget and it really matter. I rather tell on phone and them decide I over budget than give up time in person for interview and find out then.
Those people who price matter to, might wish they could go to someone over their budget but it rare the extra service suddenly make them have more to spend. I might go look at expensive car and able to see why it worth extra cost but it not mean I suddenly able to afford it.
I understand your main goal but parent also have goal of their own. And if that include a set budget and you are more, why waste everyone time?