You can pick them up quite cheaply in decent condition. It's very rare that examples sell for over £100 (Tim Everson's collection being the exception where the combination of the person who wrote the book coupled with some decent provenances pushed a few pieces very high), with VF to gVF examples appearing for tens of pounds. Like Peter, I would subscribe to the idea that although £2 for 4 is only the cost of a pint, for the cost of a round you could get something that you would want to keep long term.