Thats a neat design, but its a bit disengenuous to say its not switched mode... it is a switched mode regulator, but I take your point that its not AC line level switching, therefore safer. That chip is good to 60v so a 0 - 50v variable supply at 5A (for a single chip) with low heat output is very possible, and using tapped inductors a 0 - 25v at 10A with a single chip is possible... interesting that the Elektor approach used two chips for 6A when they could have done it in one by winding their own coil instead of buyng off the shelf... think they missed a trick there... the chips are £9.24, the ferrite a lot cheaper...

However, it still doesn't overcome the OP's initial issue - the cost of toroidal transformers...