Growing my own veggies...
Honestly, I can't grow the basics like cabbage, onions or potatoes cheaper than buying from a bulk/warehouse store. However, it's worth it for the more expensive things like tomatoes, kale, pumpkins, squash, beets, arugula and herbs etc.
Sewing my own clothes...
With the flood of cheap clothes from overseas sweatshops, it just doesn't make sense to sew your own at least for the more trendy items. The cost of fabrics and notions have skyrocketed, perhaps because sewing has fallen out of fashion. Now, I use my sewing machine to customize pre-made items like IKEA drapes, do my own pant hemming, and mend my good quality clothes.