I'm a woodworker by trade so my work can be somewhat seasonal. When I have money it's because I'm busy with work (too busy too DIY camping gear). But when winter comes and work slows down,it makes sense to DIY. Price wise it doesn't save much, or any. The benifit is making EXACTLY what you want, for example I love my 6'6"X12' digital camo hammock, I wouldn't be able get one of those off of the shelf. Where thread injecting is like money in the bank, is for mods and repairs. I especially make a lot of repairs to my upland hunting clothes (damned barbed-wire). I've also repaired straps, packs and other clothing. I also like getting the same sort of satisfaction, when thread injecting and working with my hands, as I do while woodworking.
P.S. Usually my dyslexia is a pain but sometimes it gives me a chuckle; I read SelfMadeHiker's name as SelfMadeHitler and I thought what a terrible name no one will ever give him advice