The tree you need to be barking up is @mikeV but he’s been fairly MIA lately.

If it is not selling for what you think the market value is then is there anything particularly undesirable about this property (neighbor has three white vans in the front yard and dogs that bark all day and night)?

I live next to an airbnb property and it is quite annoying, all the things the neighbor complained about happen on a regular basis and I don't complain because nothing will happen, just as in your case there is nothing obviously wrong with someone skateboarding up and down the driveway at 9:30 at night but it still gets annoying, and gets my dog barking every time.  

Nevertheless, you’re barking up the wrong tree.

Noise complaint from neighbors about barking too much

Just remember to keep in mind that when you buy a place you are buying your neighbors too, barking dogs and all. 

All bark, but no bite. 

We then add a bunch of motion activated dog barking sound makers that are cheap on amazon.

So far I've gotten a 15k quote for architect/engineer, and contractors 'pall-bark estimates' (they cant give firm estimates without a formal plan) from 250 to 500! 

There are some that bark about Constitutional Rights, they lack a basic understanding of Rights of the State to control commerce and being in the business of means you are under consumer and commercial compliance requirements, like it or not, that is the reality that must be dealt with.