When I was new I looked at the stuff for sale and said "no way, I can do that for less." Turns out it cost me more, much more, but it was tailored to the types of risks I felt were most probable.
Something similar happened to me with my car kit. I ended up spending perhaps four times the cost of a pretty comprehensive pre-packaged kit. But then of course I got good quality items, including some that are not commonly available. The sturdy Carhatt bag alone was $40 or more.