There's a few considerations-
The equipment costs on what you have described is about $4800. That includes furnace/air handling section, cooling coil, condensing unit, refrigerant piping, Flue piping, some duct insulation, tape, mastic, screws, possibly a new outdoor plastic equipment pad.
Then there's a truck/van, tools, drill bits, insurance, vehicle maintenance, classes to keep up to date and other consumables.
This job typically takes about 12-16 man hours of highly skilled labor and 12-14 hours of "helper" labor. Combined hourly rate is about $125 that includes payroll, health insurance, vacation, profit and overhead. So that's about $2,000 in labor costs.
$5,000 + $2,000 = $7,000.
Tack on that "5 years of all maintenance" and "10 years of warranty on just about everything" and I think $8500 is about right. Nothing is free. That 5 years of maintenance is worth about $900, insurance (warranty) for 10 years is probably about $1,000.
NOBODY is getting the equipment you specify in Florida or anywhere else for $4,000. No one. You can't even buy the equipment for that price.
Also consider that there's fewer and fewer people entering the trades every single day. That means there's less people to perform this labor. What's a shortage of anything cause? Price increase.