How much does it cost to fix an OpenCart bug?

A single, well-defined OpenCart bug starts at $99 (a Quick Fix, ~4h @ $25/hr) and ships in 24-48 hours. A batch of related bugs, or one deep root-cause like post-upgrade fallout or a payment-callback failure, is a Bug-Fix Sprint at $499 (~20h @ $25/hr) with full regression testing. Stores that need round-the-clock cover take an Emergency / Retainer; a full stabilization sprint is around $2,499 (~100h @ $25/hr). You always get the quote before any work starts.