I think the gallery plug was something on the order of $11.

I didn't use a sandwich adapter because 1) It lowers the oil filter by about an inch. I'm all for as much clearance on that as I can get due to offroading (your results may vary) and B) It gives me a temperature reading inside the engine, not right after the oil cooler, which is where the sandwich adapter will be. Keep in mind I'm referring to temp and not pressure.