I suspect that it's going to be location dependent. 

I suspect appraisals can  be somewhat influenced by the person purchasing the appraisal, especially if there is no sales contract involved. 

That seems like a huge percentage when I suspect they are providing you some purchased lists, some potential buyer lists, maybe some marketing, maybe a mailing budget.  

I had a tenant who I suspected was doing drugs in the unit. 

Tenant is rightly suspecting you do the bare minimum for a premium price.It caught my eye that you said a few times “we never used it” so what?

I suspect some of the calculators are just rounding to the closest whole number.

This amounts to extra cash flow and should be considered in the decision to sell.Note as PM, 8% of rent you are earning by managing the property.I lean toward selling not because I do not expect the property to produce a good return but because I suspect you should be able to do better. 

I suspect most investors using other people's money have developed these tools over the years with experience, money, and sweat equity.

One non-destination location type of Airbnb that I have booked that I suspect are reasonably successful are guest suites, ADUs, etc in homes off of highways or between / near destinations.

I suspect yes, so what are their rules and policies?