How much does undertale cost?

That depends on the device. Undertale costs $9.99 on Steam, $14.99 on the PlayStation 4, $14.99 on the Nintendo Switch if it's the standard edition, and $44.99 if it's the collector's edition. The Undertale Collector's Edition is sold through Fangamer and includes a physical copy of the game, a collector's box, a story booklet, a soundtrack, a sheet music booklet, and a music box locket.