This thank you card by Terrapin Stationers & Engraving Co. keeps it short and sweet.
The card simply reads 'K. Thanks. Bye.' Because at the end of the day, what else really needs to be said? According to Urban Dictionary, the phrase "kthanksbye" is "Used by savvy Internet users who wish to create a sense of conclusion with a short and to the point phrase." If you, too, wish to thank someone in a direct and to the point manner, then this brief thank you card will do the trick.
Of course, the terse punctuation and use of the word "bye" may make the card a little brusque, rather than overflowing with gratitude. It's probably best reserved for best friends, or co-workers whom you wish to thank passively-aggressively.