Plug in your scrap volume, yield, electricity price, and time cost. Get payback months + spools needed. This uses scenarios because real-world numbers vary (and may be unknown pre-release).
Usable kg/month = scrap_kg × yield
Gross savings = usable_kg × new_price
Electricity = usable_kg × kWh_per_kg × electricity_price
Time cost = usable_kg × hours_per_kg × time_cost
Net savings = gross − electricity − consumables − time
Payback months = (machine + shipping) / net_savings