Silica's Gratitude card prices

Why Silica's Gratitude has 4 prices

Each printing is a different physical card — a different set, number, often a different frame or foil treatment — and the market prices them separately. The range above runs from the cheapest priced printing to the most expensive one; the chart follows the most expensive. Open any row to see that printing's own history, every foil variant, and where it costs less.