According to a Volkswagen dealer in Cape Town, a whopping R6 800 on top of the price of a Touran.
Or, according to a Toyota dealer, R2 500 more on the cost of a Verso.
But, say Goodyear and Continental, who make and market run-flat tyres in South Africa, both these prices are exorbitant.
And what was not mentioned to the potential buyer, in either case, was that run-flat tyres should only be used in conjunction with an on-board tyre monitoring system to warn the driver when in fact, he or she has a flat.
According to Continental's Rodney Idris, run-flat tyres retail at between 15 and 18 % more than the standard tyres fitted to a vehicle.
That means that, according to the VW dealer's quote for run-flats, it costs around R45 000 to replace a set of standard Touran tyres!
Even the Toyota works out pricey. Based on the "options" price for run-flats quoted for the Verso, this means a replacement set of standard tyres would set you back around R17 000.
Both these are way out of line.
Idris adds: "The need for a pressure monitor is essential as you have indicated.
"I have heard of instances where monitors were not fitted and tyres have been run well beyond their safe distance as well as speeds well in excess of the recommended 80 km/h, with near-accident situations arising as a result.
"We do not recommend the fitting of SSR (Continental run-flats) tyres without a Tyre Pressure Monitoring System being part of or fitted to the vehicle."
There are positive and negatives associated with fitting run-flat tyres.
On the positive side, you can carry on driving for 80 km at 80 km/h when you have a puncture without having to stop and change a wheel - an obvious advantage late at night or when travelling in remote areas.
The tyres also stay on the wheel in the event of a blowout, giving better control and most certainly giving the driver better chances of avoiding an accident.
On the downside, the run-flat tyres should not be run deflated for more than 80 km, at a maximum of 80 km/h.
And they must be discarded after that - they MUST NOT be repaired.
Secondly, not many tyre fitment centres offer a 24/7 service, although ordinary tyres can be used in place of run-flats to "get you home".
Thirdly, there are some issues with ride quality on run-flat tyres - although I am assured this has improved with the latest tyres - as well as the higher price of run-flats.
No matter what your reason for wanting run-flats, here are the essential facts:
1. They should not cost more than 15 to 18% more than standard tyres
2. You MUST have an on-board and functioning tyre pressure monitoring device.
My take on the issue?
It's a highly-competitive world out there, and motor dealers are scratching to make money, especially on new cars.
What seems to have happened in both the cases mentioned here is that the dealer has offered a discount on the price of the new vehicle, then tried to claw it back by charging well over the odds for the run-flat tyres.
If it's happened in two cases, in two totally different dealerships, then my bet is that it's a pretty widespread practice.
In both cases the salesmen pulled out brochures outlining the benefits of run-flats, but not mentioning things such as replacement costs and tyre pressure monitors.
By the way, there are also a number of other "dealer options" that are mentioned on the dealer's quote, such as special protective polish, at R750 a shot, as well as other charges for "delivery" and so on.
I would not suggest you put ANY polish on a new vehicle until the paint has had a chance to harden properly. Some manufacturers recommend as much as six months before you apply polish.
Tell the dealer to take a hike!
Oh, and watch out they don't try to charge you for something called "documentation fees" or something similar.
I've heard of as much as R1 500 being slapped onto the bottom line for this one, and for the life of me I can't see what it's for, except to pad out the dealer's profits.
Again, tell him you're wise to this, and threaten to go to another dealer if he insists on keeping it on the bill.
He'll quickly drop it!