Frugality isn't about individual products, but about lifestyle and needs.
Product X isn't always better or worse than product Y, it's all relative to your needs. For example, if I'm on vacation, I'll buy the single use can opener from the dollar store instead of a nicer one that could last years. But if I'm at home, I'll buy something that lasts a lot longer. Maybe you'd pick X in one scenario and Y in another.
As for shoes vs bike vs car, here's a concrete example. I used to work about 10 miles away, and the company was located right next to a bike path that connects near to my house. My options were:
- bus + nicer pair of shoes - bus was ~mile from my house, and dropped me off right next to work - total trip time ~1 hour (20 min to the stop, 40min on the bus due to a transfer), a bit more in the winter (we get lots of snow)
- bicycle - 40-60 min year round (ride to the bus in the winter); cost $500-600 (dependable and has rack mounts)
- car - 20-40 min year round, depending on traffic and road conditions
Average costs over 5-ish years:
- walking - $100 for shoes + $4/day (no annual pass options; 250 days/year) for the bus = $1100
- bicycle - $600 for bicycle, $30/year maintenance (two chains/year, one cassette over 5 years), ~$50/year bus fare = ~$1000
- car - will have one regardless (need for road trips), so my estimate is something like $0.25/mile in extra costs beyond the insurance and registration I'll pay anyway; so that's ~$1k per year
So cycling and walking+bus are about the same price, and I can use the bicycle for trips to the store and whatnot, so I went for the bicycle.
If my commute was longer, the bicycle would be impractical unless there was a good train line or something. If I lived closer to work (say, 1-2 miles), I'd just walk. But for that situation, the bicycle was the cheapest long term option that met my needs.