histerik gets the punchline but Peacemaker gets the situation reference as do I since my family lived it. In 1979 Grandma was downsizing and sold a 7 bedroom 2 1/2 bath big home that was one block from the beach in a preppy Mid-Atlantic US seacoast town for the then huge sum of $99,000!!!. By 1986, only seven years later and within the time frame of this Dilbert era, the same house with no improvements, was listed for $286,000! It was purchased by a husband and wife lawyer couple who modernized and renovated it (but did not increase the square footage) by 1990. The last time my relatives saw it listed for sale was in 2007 for $1.7 million dollars...
This strip is the kind of thing that you won't get unless you were around in the real estate booms of the seventies. This strip was written in 1989, but we are reading this in 2009, and the real estate boom is over, as evidenced by the global economy over the past five years or so. Therefore, less people understand this and find it funny.