Here is how you can find out how much your neighbour's house sold for without asking them. Well, the obvious answer is to call me, but one of the options for viewing sold data is how sigma.com, but it's only available in Ontario and BC. They have an app and a website that provide accurate sold data to home sales.
In BC and Ontario, all you have to do is create an account and you're able to see all the details of a sale. But if you live outside of Ontario or BC, it's a lot harder. In some provinces, real estate agents have to pay fees to access sold data, so the easiest and most reliable way is to reach out to your local real estate agent.