That's a great post card, How can it really bite him in the ass. He is smart for not discounting his primary service (carpet cleaning).
Its also smart to give them something of value free(Teflon). Next time his client calls with out the free Teflon offer, guess what its pre sold! "we can apply the Teflon protector we applied for you last time Mrs Jones for X amount of dollars"
That's how I made my job average go from $88 to over $250 in less than 3 years.
The best part is it should drum up business during the slower season and not effect his job average, especially if they want to take advantage of the free Teflon on the furniture, they have to pay to have it cleaned first.
The bottom line is to make the phones RING! Many people call from postcards in my business and forget to redeem them any way, and they don't even care.