13 bucks is pricey? Thats cheap, for such a good valve. But, you can build a higher performance piston valve for cheaper, if you have the knowledge and skill.
Is it really necessary to put Teflon tape on the valve? Because if i ever make another one i might want to be able to remove the blowgun to put it on other valves.
Teflon tape is not an adhesive, so sticky properties. Don't let the word "tape" fool you. It just wraps around the threads to seal it. Blowguns are only 7 bucks, and taking it out only weakens the threads, so I'd just get a new one if you need it for another project.