You’re taking the metaphor way too literally. The people who made the most profit weren’t literally selling shovels, they were the ones providing logistics and support services to the gold miners, like hauling tons of equipment over tens of miles of mountain or providing the sales channel for the gold. They siphoned off most of the profit from the ventures that depended on them (like LLMs depend on GPUs) because the miners had no other choice, to the point where even the most productive mines often weren’t profitable at all.

A less literal example is the conquistadors: their shovels were ships, horses, gunpowder, and steel. You can look at Spanish records from the Council of the Indies archive and any time treasures were discovered, the price of each skyrocketed to the point where only the wealthiest hidalgos and their patrons could afford to go on such adventures. I.e. the cost of a ship capable of a cross Atlantic voyage going from 100k pieces of eight to over a million in the span of only a few years (predating the treasure fleet inflation!)

Gold rushes create demand shocks, and anyone who is a supplier to that demand makes bank, regardless of whether its GPUs or “shovels”.

GPUs don't really have six year lifespans, though. The hardware itself lasts far longer than that, even hardware that's been used for cryptomining in terrible makeshift setups is absolutely fine for reuse.