Seems like that's everywhere, E-bay is just a better known forum... Because of the inherent differences in the Jeep engines, and general design, there is a huge market for "performance Jeep parts", or just parts that your engine doesn't even need... Case in point:
Valvoline Instant Oil Change (yes, there was a time when I didn't change my own, that was the turning point, and getting bigger tires so I could get under there easier): Tells me that I need a new PCV valve, mine is totally gunked up, the little float ball is stuck, and it'll help my fuel economy so much... Last I checked, the I-6 had no such things, just the little CCV elbows, with no floats...
Murray's Discount Auto Parts : Suggests rear brake rotors along with my fronts so that they will wear evenly... Were there any stock '00 XJs with rear disc brakes?!?
AutoZone: Lets me know that my '02 Model Year Cherokee won't scan under the proper setting, they have to scan it as if it were an '00, so I should probably have the computer checked... '02 Cherokee?!?
Oh yeah, and there's the classic at Belle Tire, telling me that they did the look over for the engine, and would I like a new cap, rotor, and wires installed, because mine are looking a little worn... Hmm... And just where would you put those exactly?!?
So a 15 dollar fan being sold as a performance part exclusively for the Jeep?
Nothing special