In all likelihood, you'll have spent an awful lot of money on Steam games over the years---you can find out exactly how much by using the Steam Calculator or Steam Gauge (turns out I've spent over $4200). But have you ever wondered what are the most expensive items on Valve's platform? Thanks to Kotaku's Nathan Grayson, now we know.

It probably won't come as much of a surprise to learn that the costliest product on Steam isn't a game but an application. Technically a piece of DLC, Strata Spaces VR---Professional Edition Upgrade is designed for modelers and designers who want to see their creations brought to life in virtual reality. At $995, it's not a cheap process. If, however, you were to buy all of a title's available DLC in one go, the $4207.42 it would cost to own everything Train Simulator has to offer would make it the most expensive purchase on Steam.

We know that microtransactions can quickly rack up large bills, but for a single punch to the wallet, nothing beats EVE Online's package containing 15,400 of its PLEX in-game currency, priced at a whopping $500. Similarly, the most expensive custom character you can buy is RimWorld's Pirate King upgrade for $370. This lets you enter a name and character backstory into the game, with skills, appearance, and special work requirements. Additionally, this character will appear as the leader of another faction.

As they're packed with numerous different titles, game bundles are understandably expensive. The priciest of these is the Rebellion Anthology. It includes games such as Evil Genius, Sniper Elite V2, and Rogue Trooper, though it's mostly made up of DLC packs for the Sniper Elite series. The collection usually costs $463.51, but it's currently discounted to $379.99

People may mock Apple's attempts to sell a $300 physical book, but it might not be as bad as Star Story: The Horizon Escape's art book; a PDF that costs $200. In all fairness, the product is advertised as a way of supporting the game's developer.

Finally, there are the ever-changing Steam community market items. The top listings, which include trading cards and weapons for games like Team Fortress 2 and CS: GO, hover around the $1890 mark.