Cost of Tires and Wheels
I'm not an expert, but I'm guessing that $4K may not be unreasonable. The original post didn't specify what tires or rims were on that display vehicle.
Out of curiosity, I went to Tire Rack. Not being picky, I simply picked a set of rim, tires, TPMS, etc and priced it. Here's what I got.
20x9 ASA JH8 Chrome Plated $354.00 $1,416.00
245/45ZR20 Goodyear Eagle RS-A Blackwall $207.00 $828.00
TPMS SENSOR $55.00 $220.00
TPMS NUT $7.50 $30.00
UPS Ground shipping $115.00
These tires and wheels will be mounted and balanced at NO ADDITIONAL CHARGE
total $2609.
I'm not sure what it'd cost to remove your old tires and install the new set, but add those costs to the $2609. I'm sure if I chose "fancier" rims and high performance tires, the cost, with installation, could easily approach $4K.
It all depends on what your budget is and your percepton of whether or not that $4K is excessive. You gotta do your homework.
Vince.