Is $7,000 to install a whole house dehumidifier a fair price?

I'm looking for advice on the best way to install a whole house dehumidifier. My house has 2 floors and about 4200 sqft. The 1st floor has a 4-ton variable speed unit, and the 2nd floor has a 2-ton variable speed unit. The house has foam insulation. Humidity generally hovers around high 50s and low 60s when the thermostat is set to 72. I'd like to get the humidity to around 50%, mainly for comfort (I don't have mold or humidity condensing around the house). The HVAC technicians I've consulted have all recommended a unit between 100 and 130 pints, installed in parallel on the return for the second floor AC unit. I'm seeking advice on whether a unit in that size range, connected the way they are describing, would work.