They have to be the best bargain you can get. A Hunter is cheaper than a new PA28, shares in jets are available for as little as £4000. The spare parts are cheaper ( a viper engine runs in at £7,000 instead of £20,000 for a new continental).
Sure fuel is a bit more expensive but you are going a lot faster in something fully aerobatic. Just ask yourself the question, 1 hour in a jet or 5 hours in a PA28 (yawn). Which would you choose?
You don't even need a PPL to join if you are willing to fly dual all the time.
Do it and keep these beautiful historic aeroplanes flying.