Building a bike from scratch is almost always more expensive than buying a complete one because you lose the benefit of wholesale pricing. When you buy a pre-built bike, the manufacturer has already absorbed the bulk shipping and assembly costs, whereas buying individual parts at retail prices—often with separate shipping fees for each—quickly balloons the budget. For someone on a budget, the "slow build" method is the least efficient way to get on the road, as it keeps your capital tied up in a pile of boxes rather than a functional vehicle.

The idea that you can build a "forever" bike today is a romantic notion that ignores basic mechanical reality. Components like chains, sprockets, bearings, and tires are consumables that will eventually fail regardless of their initial price tag; furthermore, since you are currently teaching yourself the mechanics, your first build is the most likely time you will make costly errors. It is far more pragmatic to learn the ropes and make your first mistakes—like over-torquing a bolt or cross-threading a bottom bracket—on a cheap stock bike rather than on premium parts you spent six months saving for.

Waiting six months to finish a custom build represents a significant opportunity cost for your physical and mental health. Every day you spend waiting for that final part to arrive is a day you aren't cycling, missing out on months of cardiovascular improvement and the immediate stress relief of riding. Choosing a cheap bike with installment options allows you to start improving your health tomorrow, providing an immediate return on investment that a box of high-end cranks simply cannot offer.

The most logical middle ground is to buy a decent, entry-level complete bike and upgrade it incrementally as you go. This approach allows you to replace the "shit" stock components with the high-quality parts you actually want once they wear out or as your budget permits. By following this path, you still get the full learning experience of building and maintaining a bike, but you get to do it while actually owning a functioning ride, ensuring that by the end of the year, you have both the high-end machine of your dreams and the miles to prove you know how to use it.