About and method
UnitBasis is a small static index of Amazon products ranked by a single unit price. It is not affiliated with Amazon, except as a participant in the Amazon Associates Program, and it is not affiliated with diskprices.com or any other comparison site.
Categories in this first version: power banks in dollars per watt-hour, protein powder in dollars per gram of protein, and AA/AAA batteries in dollars per watt-hour. Those units can be computed from the product label plus a verified price. Graphics-card dollars-per-frame is out of scope because it needs a third-party benchmark database.
A numeric price is published only after a verified fetch from Amazon's official Associates API (when the account is eligible) or from a dated manual check made with official Associates tools. Automated scraping of Amazon product pages is not used.
Watt-hours for a power bank are taken from the label when present. If only milliamp-hours are stated, watt-hours are inferred as mAh × 3.7 / 1000 and marked as inferred. Inflated capacity claims, when they can be flagged from the label, are not allowed to sit at the top of the table.