I agree with
@Bennoel 10 . If I am seriously interested in a car with no price I will inquire. Usually in this circumstance, the price is too high but not always. For me, asking price is just a starting point for negotiation anyway. I also agree that many times no price is listed is because it's a stupid high price for what is being offered. I have a buddy selling a car right now and he put vinyl stickers at the top of the windshield and rear glass stating 'for sale' and his phone#. No price, no info. Nobody calls from that. He also printed detailed flyers with complete info and pics, but no price that he leaves under the wiper when parked. Got a couple calls at Hot August Nights but they ended when the callers heard the price, which is too high for the car. What is the price you ask? $30k last month, $25k last week, $27k to the last caller, $28k to the next caller, $22k this week, etc. He's fishing.
When I hear a price that's ridiculously high I'll just say, 'let me know if you decide to sell your car instead of advertise it', and leave it at that.