I'll do a full post tomorrow, but I just wanted to say YES! I've finished all eight of the dice towers.
Now it's a matter of finding homes for 6 or 7 of them. I wonder what people will think they are worth?
True cost - in terms of materials and tools, but allowing nothing for labour - probably amounts to about £45 each. Labour-wise, each one probably took about 2-3 hours (including the design work - by the end, I'd got assembly down to under an hour).
One of them squeaks a bit when folding up the dice tray (I'm guessing some glue got into the hinge part), and another just looks a bit scruffy around the joins (better than all my previous dice towers, but not as good as it's 7 siblings - I'll sell it half-price as a "factory second").
But overall I'm very happy with the results.