Wildly different quotes for new HVAC

[chuckee]

Hi,
I need to get an HVAC system completely replaced for a cheap rental in Memphis (house value around $30k).
I've been give a quote of US$2944 from the property management company:
Quote to install new 3 Ton System
3 Ton Condenser
3 Ton Coil
72,000 BTU Furnace
AirTemp System. W/ 10 Year Part Warranty 1 year


I then got another quote from a separate HVAC installation company, which was for $7877, for the same thing.
This seems ludicrous - any idea what that quote is about?
Is it common in the USA to be given outrageously high quotes, in the hope that they will just be accepted without the property owner doing multiple quotes?

[John the builder]

you could also be getting better value from the higher price. Maybe the lower price is just that

What business are you in and do you set your prices?
why am I not allowed to quote what I think the jpb is worth? You dont have to accept it?