Depends on what you get. Some of that cheap shit like RActive is poorly made and can break on you. How would you like to go down the road and your shitty RActive coil come out? It could happen. A company isn't going to take the technology and materials and effort to make products that are as good as expensive stuff and sell it cheap.
Like swap bars, for my car (see sig), they have some cheap ones that dont even align up right, they are known for breaking and ripping shit. Of course, they are stiffer than stock, but they suck.
Cheap struts will bounce around, might even increase body roll. Image you out on the highway, doing 75 (it the limit herE) and a gust of wind comes across the highway and your car starts bouncing you losing control? Welp, you totalled your car, could have killed you and someone else, all over saving a few bucks.
IF you purchase cheap stuff and something happens, just remember, its ppl like that that feed cali and other states and some congress people to have "to low" laws and other things.