The enthusiasts for state housing tend to repeat untruth so frequently they may come to believe it themselves. Sorry, but No:
Building a house pre-war may have cost a thousand pounds or less. But as a proportion of average income, that was an enormous amount of money. A smart five year old can figure out that a 'Thing', of any kind, which is worth the same as ten Mars Bars has a value of ten Mars Bars. If currency has devalued, to the point where the same 'Things' now cost one hundred Mars Bars, then said 'Thing' a) has not been fully paid for, if only one Mars has been handed over, and b) will still not be fully paid for, even when ninety nine Mars Bars have been handed over.
Inconvenient Truths:
Opportunity Cost Of Capital Invested. (This might need a smart 8 year old) At the time you invested all available pocket money savings in Mars Bars, which produced no 'Interest' or 'Profit' at all, you could instead have invested in all kinds of other things; Stocks and Shares, Land, other profitable income-producing investments, not least, buying a sweet-making factory, or in this case, housing which was let out at Market Value Rent.
That way, if an average person on average earnings was able to spare two day's income a week for rent, that would be the rent agreeable to both sides. It would be a peculiar investment to deliberately and permanently set a rent of only half that, ensuring no return on the capital, and no capital reserves for future major repairs and refurbishment and maintenance. It is wilfully silly to declare that council houses are 'free', because they were built long ago. Are other houses 'free', built at exactly the same time?
Variation in the Rental Value and in the Resale Value (A smart twelve year old could grasp this) You built homes in lots of areas.
But currency devaluation, all on it's own, now makes the cost to buy them a hundred times more than they would have sold for on the day they were built. The same difference applies to the difference in a rent between now and the day they were built; i.e. Their rental value is worth a hundred times more than they would have rented for, simply because of successive governments' abandoning the gold standard and printing money.
A second variant is that many of the areas where you built houses will have become more fashionable. When an area was run down, derelict, a bit dangerous and un-cared-for, the market price to rent or to buy a home would not be particularly high. If it becomes highly desirable, with rich people eagerly competing to live there, then obviously the real market value of a home, to rent or buy, will be extremely high.
(There is a legal case which ought to be taken, when LA housing bodies refuse to make best use of their assets, as they ought under their Public Service Duty. One example was a site bang in the centre of a luxury area, right next to a B.R. station, right in the centre of the extremely trendy village. Achieving millions per house is easy. Developers could have traded a hundred houses to be council homes, within a short distance, for every plot permission in that prime site. Instead, the L.A. dogma allowed them to erect a council estate of one house per plot worth it's size in gold bars.)
A third variant is that all governments' interference in operation of the housing market has deliberately boosted prices, (using every means including encouraging unsustainable debt, pouring in money from the public purse and altering tax rates) In turn inevitably, this has boosted the market level for rents. Making a return on investment, for a private landlord, must be a mathematical sum based on the cost of the property. (Duh)