When somebody doesn't want to give me a price, I've started asking them for an order of magnitude. Sometimes they still don't want to say a number, but when I ask "is it 2$, 20$, 200$, 2k$, 20k$?" they will usually give me a ballpark, along with the factors that'll make the price vary.

It's a balance, they might not know exactly what the job would entail until they send someone to look, and labour could double the price if it's something ridiculous.

However, they absolutely should be able to give a ballpark, and it drives me up the wall, especially when I've given enough details for them to do so.
I hate it.
If you won't even tell me how many zeroes your service is going to cost, there is an absurdly high change you're going to be wasting your engineer's time doing a visit.

"How much for a 12000 BTU on the ground floor with electrical already run?"
"Well sir, we can't give an accurate number yet, as we need to send someone out"
"Not even a ballpark?" "I'm afraid not sir"

Which led me to investigating what I could do myself...Turns out, they now make self-install units for about £600.
Or Costco sell a better brand one including fitting for £1500.

say you want the condenser unit placed on your roof or backyard. the routing would be completely different. Say you have an unfinished basement vs they have to remove and replace a shit ton of drywall. completely different. the unit itself is a static price. the conditions of installing the unit are a huge factor. is it on a drywall wall or are your walls all poured concrete?

There is a lot of info they need that frankly you can't trust the average client to accurately give over the phone. They need to know what your walls are made of, are they concrete, brick, wood or metal stud? Are they going to need masonry tools? What is the interior wall material; asbestos reinforced plaster is still not uncommon in older houses and if they're working with that the the price goes up dramatically? Is there electricity run to that location already or will they need a new circuit? If there is electricity run to that location does the existing circuit have capacity to handle the load? Is there even available space to mount the new unit? Is it in a neighborhood where it will need a cage around it to deter theives? And that's only some of the info they need.

About the only accurate price they could give you over the phone is the cost of the unit itself which you could also just find via a google search. The actual labor and other costs will vary by orders of magnitude depending on certain conditions.