Raised Beds - the question

Raised beds: leaving aside the subtle questions of dimensions and the complicated analysis of what goes where and assuming we have already decided the benefits of raised beds outweigh the cons the only thing left to decide is material. That is what should the raised beds be made of. Now in theory raised beds can be made of almost anything you like - some things being more practical than others - I suspect lego beds wouldn't stand the internal stress (but then James May's house of lego worked, at least in the short term).

Our raised beds are obviously intended to go in the community garden. Our motto is "form follows function" so they need to be functional, that means hardwearing, durable, non-toxic, longlasting but part of the function of the garden is to look nice and be a nice place to sit so the raised beds can't detract from this by being extremely ugly either. This rules out some of the obviously cheap but rather ugly building materials.

We had decided on railway sleepers - not the recyled/reclaimed type which are generally filled with creosote residue and pretty toxic - but the nice new sort, freshly made untreated but still looking for all intents and purposes like the railway sleepers of yore. However if you start piling these up to get some height into your raised beds, as we intend to do they start to get pretty pricey. Effectively a 1m high raised bed is the same amount of raised bed building materials as four 25cm raised beds and four times the price. - So inexpensive needs to be added to our list of requirements.