Diy- cost effective? Ha! Never!
Worth doing? Always!
Financially, most are better off working and paying the pros for their time instead. But...
...if you can
make it, have the time to make it and will enjoy end result then do it.
I love using my own made kit, much better than bought as it gives me a bigger grin.
The only bits of kit that I've made that was cost effective was my Underquilts, single layer hammock and a few saws-I did save money, but only just. As they won't fetch much on resale, you potentially lose money there too.
Homemade kit is terrible for the wallet, great for the soul.