I agree. The more logical mixup would involve the first two letters of each word: "P" (if it's "Pleasure") or "T" (if it's "Treasure") and the "K" for kill. Following that logic, you would get, "It will be a kreasure to pill you." As I'm not aware of the existence of the word "kreasure", and neither were the writer's, apparently, they left it as we see it in the film.
Another thing I found interesting is that Fred Draper played the murderer in the most previous episode, "Last Salute to the Commodore" and had a significant role. His reward? He gets the shortest follow up appearance by any murderer in the Columbo series: one line - LOL!