I see a lot of specific examples, but here is a good engineering guideline: do not skimp on physical interfaces. **Anywhere energy is changing form or if it touches your body, don't skimp on those. **
For example
tires
bicycle saddle
heaters/furnaces
electrical inverters
keyboard
mouse
engines
shoes
eyewear
clothes (buy used if necessary, but always buy quality clothing)
Quality usually means more money, but sometimes one is able to find a high quality and low-cost version. In my experience though, trying to find the cheap version that works well means trying so many permutations; it would have been more economical to just get the more costly version in the first place.
More expensive doesn't always equal better, especially for things like keyboards, clothes or eyewear, where branding is huge and inflates prices more than quality.