I raced in the Porsche 924 series for a couple of seasons. Same idea; cheap racing and close competition. The suggestion was that you could buy a car for £1000, put a roll cage etc. in and off you go. It was obvious that people were spending big (6 figures!) money on the series and even then they weren't winning. It cost me in excess of £8000 to build a car from the previous one I'd written off. The idea of cheap racing is very appealing but in reality it's very hard to do. Time Attack should be cheap but it's not.
If you want to race cheaply, look at anything organised by the 750MC, particularly their MR2 series.