GM dealers "close" to me are all 15 miles away. That means at least TWO trips for me because the dealer doesn't stock them. 60 miles total drive time, so lets say 20/gal because this isn't a highway to highway drive for me. So at $3.50 a part, another $6 for the gas, I'm now up to $9.50. And guess what? that's also another hour of my time to deal with said drive. Or I could send $15 to someone via Paypal, and get it mailed to my house. That extra $6 was WELL worth the time I saved in driving and dealer interaction.
