How We Calculate Payoff Time
Our formula is simple, transparent, and consistent across every article. Here's exactly what we do.
The Core Formula
Every payoff calculation uses the same basic formula:
// Breakeven in months
breakeven = product_upfront_cost / (alternative_monthly_cost - product_monthly_cost)
// Annual savings
annual_savings = (alternative_monthly_cost - product_monthly_cost) × 12
Our Assumptions
We always state our assumptions clearly in each article. Common assumptions include:
- Usage frequency — how often you'd use the product (daily, weekly, etc.)
- Alternative cost — the ongoing cost of the status quo (we use current median prices from Amazon and major retailers)
- Product longevity — we assume products last their rated lifespan
- Ongoing product cost — consumables, maintenance, electricity, etc.
Price Sources
Product prices are pulled from the Amazon Product Advertising API at build time and cached. We refresh prices weekly. Alternative costs (e.g., "cost of takeout twice a week") are researched from current Bureau of Labor Statistics data, restaurant industry reports, and major retailer pricing.
Sensitivity Analysis
Every article includes a sensitivity analysis showing how payoff time changes under different usage assumptions. We use the median usage scenario as our "base case" and clearly label it as such.
What We Don't Include
We're explicit about what's out of scope in every article:
- Time value (the "opportunity cost" of time spent, e.g., cooking vs. ordering takeout)
- Quality-of-life factors (convenience, taste, enjoyment)
- Environmental costs/benefits
- Financing costs (we assume cash purchase)
These factors matter — we just can't quantify them cleanly. We mention them in the "Fine Print" section of every article.
Honesty Pledge
PayoffTime uses Amazon affiliate links. We earn a commission when you buy through our links, at no cost to you. This does not affect our calculations or recommendations — if something doesn't pay off, we say so.