well the cheapest to set up, has to be the recycled plastic bottles! BUT very ugly.esp with labels still on bottles
the hydroponics, looks nice, but certainly NOT attractive/pretty. Obviously with that, there is quite a lot of cost involved. Even if all parts neeeded are already available, there is the elec cost, which may be negligible ( or not, I have no idea!).
The nicest looking is the tower!
I was going to make myself a tower ( old pvc drainage pipe, cut holes/pockets for strawberries.
Also with a tower type system( dependant on where placed etc) it could potentially be rotated for Min/max sun exposure dependant on plant needs etc, if a variety is planted.
Incidentally, though not totally relevant ( or maybe it is) I understand that hydroponic growing is NOT permitted in (official certified) organic growing. Well not here in Spain, so presumably nowhere in E.U.
well having seen the tower link, am going to have a rethink and see if I can adapt what I have to make it similar, although I suspect taht one would need to be careful about what is put in the composting bit in order to satisfy plant requirements, and not overload them with something potentially damaging