Cost of purchasing of houses

I have always thought that the taxes and other costs related to the purchasing of a house in Spain is bad for the mobility.

If, for any reason, a family want s to move to another city or area, but  keeping the same level of living, one would think that the income from the sold house should cover the cost for the bought house....
However, that is not so, as the state and other involved agents, will claim their part (for instance a 8% tax, sometimes, erroneously called "VAT" of the value of the house). Totally, the cost for moving from one house to another (with the same characteristics) will be around 11%.
Having in mind the prices for Spanish houses, that is a lot of money... No wonder that, many times, it doesn't make sense moving to get a new job.
Also, no wonder that Spaniards talk about "A-money" ("white" money) and "B-money" ("black" money), when they talk house transactions.