system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is depreciation considered an expense in accounting?

No matter how many times I google this, I can’t truly understand it. I simply don’t get why you would consider the lost value of an item over time to be an expense. If I buy a machine for $500,000, that’s clearly an expense. Because it cost me $500,000. But if nearly the entire value of the machine depreciates over time, and I sell it for $1 many years later, how would that mean there’s another $499,999 expense for depreciation. Isn’t that just part of the original $500,000 expense?
gpt
When you buy a $500,000 piece of equipment, you trade the the money for the equivalent value of equipment. The company still has $500,000; it's just been converted from liquid cash to a physical asset.

But when the value of that machine begins to depreciate, your company has lost "money". You no longer have $500,000 worth of assets. That lost money is an expense.