When I was signing the papers for a house purchase many years ago, I noticed that the deed papers read
The Grantor «names of people selling the house»
for and in consideration of TEN DOLLARS AND OTHER GOOD AND VALUABLE CONSIDERATION
in hand paid, conveys and warrants to «me»
the following described real estate...
I noticed that I technically was buying the house for ten dollars.
The closing agent explained, "Well, ten dollars and other consideration. This is just a convention, so that the actual amount paid for the house doesn't go into the record." It also saves them from having to revise the document each time the price changes. (I don't buy the "doesn't go into the record" argument, because you can still look up the actual sale price from public records. But this back in the days before Zillow, where this sort of information was not available online and if you wanted to look up this information, you had to gasp physically visit the county records office.)
When I told this story to one of my friends who was also buying a house, he said, "Cool. I'm going to ask them to put down $20 when they draw up the papers for my house."
Therefore, according to the title transfer records, he paid twice as much for his house than I did mine.