The cost principle is one of the basic underlying guidelines in accounting. It is also known as the historical cost principle. The cost principle requires that assets be recorded at the cash amount (or its equivalent) at the time that an asset is acquired. For example, if equipment is acquired for the cash amount of $50,000, the equipment will be recorded at $50,000. If the equipment will be useful for 10 years with no salvage value, the straight-line depreciation expense will be $5,000 per year (cost of $50,000 divided by 10 years).