The Real Cost Formula

Chapter 11 from How I Turned a 3D Printer Into a Side Hustle by Dovydas Kirimas.

When I first started thinking about the real cost formula, I treated it like a small technical detail. It turned out to be one of the decisions that separated a hobby from a side hustle. A useful price had to cover material, machine time, labor, overhead, failure allowance, platform fees, and profit. A printer can make impressive objects, but a side hustle only works when those objects solve a problem, delight a buyer, or save somebody enough time that they are willing to pay for the result.

The easiest mistake is to focus on the machine instead of the customer. Printer specifications, nozzle sizes, exotic materials, and slicer settings are useful, but none of them create demand by themselves. I learned to ask a simpler question first: who is this for, what problem does it solve, and why would someone pay me rather than print it themselves, buy a mass-produced alternative, or do nothing at all? That question keeps the business grounded in reality.

My working rule for the real cost formula became: make the decision easy to test, cheap to reverse, and measurable. I would rather run a tiny experiment this week than spend a month building the perfect setup. A small batch, one listing, one local marketplace post, or one customer conversation can reveal more than hours of speculation. The goal is not to be right immediately. The goal is to collect evidence without wasting money or evenings.

I also learned to separate technical quality from commercial quality. A print can be technically beautiful and still be a poor product because it takes too long, uses too much material, is fragile in real use, is difficult to pack, or attracts customers who expect endless customization. Commercial quality means the item works, looks appropriate for its price, can be produced consistently, and leaves enough margin to justify the time around printing.

What changed my approach

A useful way to think about the economics is to divide every order into four buckets: material, machine time, human time, and risk. Material is the obvious one. Machine time matters because a twelve-hour print occupies capacity that could be used for other work. Human time includes messaging, slicing, removing supports, cleanup, packing, travel, and bookkeeping. Risk includes failed prints, returns, remakes, damaged parcels, and designs that never sell. Ignoring any of these makes a side hustle look more profitable than it really is.

For example, a part using €2.40 of material is not a €2.40 product. If it also uses eight machine hours, twelve minutes of hands-on work, €1.20 in packaging and fees, and carries a realistic failure allowance, a sustainable selling price may need to be several times the raw filament cost. The exact number is yours to calculate; the lesson is that filament weight is only the first line of the cost sheet.

The best systems reduce decisions. I kept templates for slicer profiles, customer messages, pricing calculations, packing steps, and listing photos. That sounds boring, but boring is good in a side hustle. If every order requires fresh problem-solving after a full workday, the business becomes exhausting. A repeatable process turns a printer from a demanding hobby into a small production tool.

What I watch for

The warning signs around the real cost formula were usually predictable: copying competitor prices without knowing whether their economics match yours. None of these automatically means the idea is bad, but each one tells me to slow down and measure before buying more filament, another printer, or expensive upgrades. Scaling a weak process only creates a larger weak process.

The practical next move is straightforward: build a spreadsheet or calculator and price from your own costs before checking the market. I try to finish each experiment with a written conclusion—continue, change, pause, or stop. That prevents sunk-cost thinking. A side hustle is allowed to be small, seasonal, or temporary. The objective is useful extra income and useful skills, not proving that every idea must become a company.

What made the biggest difference was treating the printer as one part of a business system. The machine produces plastic parts. The side hustle is the combination of product choice, pricing, communication, production discipline, delivery, and customer trust. Once I started managing the whole system instead of obsessing over the machine alone, decisions became clearer and the work became much easier to repeat.

Quick worksheet

What assumption am I making here?

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What evidence would prove or disprove it?

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What is the cheapest test I can run?

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What number will I record after the test?

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Examples and financial figures in this book are illustrative unless stated otherwise. Check current local requirements and platform terms before acting.

Continue this book series

• Putting a Price on My Own Time
• Why Cheap Products Can Be Bad Products