Hi Colin,
Please don't get the thought that I am against caravanning, not true, we have had many superb holidays with the caravan, but we have also had other types of holidays inc, Norfolk Broads and canal boats, cottage holidays, canvas camping, and even sailing yatch flotilla holidays etc.
Its rather like horses for courses.
Caravanning costs can be held down by the methods you describe, but increasingly not every caravanner has the opportunity to keep their pride and joy at home, and as we have seen on the forum, many caravans suffer all sorts of niggles and faults, that whilst the dealers may put them right, there's all the hassle and cost of taking the caravan to the repair shop, and insurance costs are rising quite steeply etc.
Whilst I agree that the nightly cost of B&B for an extended period would rapidly outstrip the cost of a caravan site, many B&B's and other hostelries can and will do long term deals.
Even with the savings you have identified, the annual cost of owning a caravan can still be quite significant, and for the same money there are some fantastic package deals to be had.
What caravanning has over some of the alternatives,is a degree of comfort in familiar surroundings that you control, with the freedom to take it to a wide variety of different locations at relatively short notice. Long live caravans, but you have to accept there is a cost to it.