Quality is one of the major ones, Take for example headlights. What do you think would be better quality, a set of ebay special projector headlights for $119 USD, or a set of $350 USD LED Halo projector headlights? If you guessed the $350 dollar ones then you would be right. If you placed the headlights side by side and compared them, you could tell the difference in quality almost immediately.
When you take a look at the eBay headlights almost immediately can see the lack of quality across the whole headlight. The first thing you notice is, you can see blemishes in the black plastic castings. But when you look at the expensive ones you can see that they are almost perfect
, they both have a tacky coating on the rims to hold them in the car but if you touch them then you that the expensive one have like a rhino lining and the eBay pair have coating resembling 3M rattle can bed liner. They call the reflective surface on the Red Line lights diamond cut. They call it this for a reason, because the surface and finish are almost perfect. With the cheap set the the fitment was not as nice either they were supposed to be fitted for one car but it ended up fitting our other car better. Another thing is the nice ones are pretty much a one size fits all piece because they had a smaller rim around the edge so it fits in every housing that you put the headlight into. Unlike the cheap lights which have a fatter rim so it is harder to fit them into any housing. For my application I will have to end up cutting the headlight to fit. For others this might be a different story.
Another example of something that you would buy off the internet and would have to take quality into consideration is weather stripping. For this the tables turn, the main project Mustang got the cheap rubbers and the ratrod Datsun got the expensive stuff. When you open up the cheap stuff the first thing you notice is the tears at all of the rubber joints. The rubber is all the same but the construction is very different, when you hold the expensive stuff in your hands you can just feel the quality. There are no rips, no tears, and most importantly the rubber is of the highest quality. What you as an individual have to take into consideration is what you are looking for in your final product. If you are willing to have those small things then sometime the cheaper lower quality stuff is better for you and if you are going for a perfect final product, then maybe the better parts are what you are looking for.
