Alot would depend on anothers need & it's location and ability to fullfill that need. Why would a person need your spot X where it is when spot Y may be free? Unless parking is at a premium where the spot is located it would be tough to assign value. Just like how in Boston a few weeks back someone was willing to pay $300k for a parking spot in downtown Boston. There's alot that goes into the value that would need to be assessd. You should check with a local expert to get a more specific opinion of value.