Purchase comps are crucial in the property investing journey. When you're looking to buy a property, it's hard to know exactly what the price you should pay is. Sellers are incentivized to try and get the highest possible sales price but the seller's expectations could be divorced from reality.
If you're buying a property, purchase comps can tell you how much you can expect to pay to purchase a home in a given market. Use this as a guideline to determine your offer.
If you're selling a property, using purchase comps can help you set proper expectations for how much you should expect to sell your house for. Use this as a guideline to determine your asking price.
Keep in mind that no two house is completely the same so different adjustments, even on the same street, can cause certain homes to cost much more than other homes.