Originally printed in the February 2004 expansion Darksteel, Mycosynth Lattice lived a quiet and little noticed life for most of its first 15 years. Once in a while, a new expansion would come out and make it a little stronger in Commander, which was the only place it really saw any play owning to its six-mana casting cost. Its odd effects of turning every permanent into an artifact, making all cards not in play colorless, and letting everyone spend all their mana as if it was mana of any color made it unpopular.
Its price mostly crawled upwards slowly due to the card’s uniqueness and the fact that it had only been printed once. It nearly doubled around the time Dragon’s Maze came out on May 2013 and saw further sudden increases close to the release of Journey into Nyx on May 2014 and Aether Revolt on January 2017. Following these upward jumps, the card price plateaued at its new level. Mycosynth Lattice continued to increase slowly but steadily once again, bringing it to its all-time high, when a reprint in Battlebond (June 2018) first sent it nosediving on a downward slope for the following 10 months before everything turned around.
Looking at a price graph for Mycosynth Lattice, it is very easy to pinpoint two significant events that have affected the card: the spoiling of War of the Spark at the beginning of April 2019 and the actual release of the set a month later. Correspondingly tracking the metagame data for Legacy and Vintage was a good way to determine that. The set’s release marked the point when Mycosynth Lattice went from being a card that never ever saw any play in these two Eternal formats to suddenly becoming a quite prominent sideboard card. According to MTG Top 8, over the late Summer of 2019, the card rose to a presence of no less than 18.00% of all registered sideboards. With fast mana being a little harder to come by in Legacy, the card had "only" found its way into 6.20% of all major event sideboards in that format by the end of August 2019.
After all that's been said, it's now time to take a look at the elephant in the room. Of course, it's not really an elephant, but a planeswalking silver golem named Karn, the four mana planeswalker from War of the Spark (April 2019). Without Karn, the Great Creator, most Magic players (outside the few Commander players actually using it), would never have given much thought to the existence of Mycosynth Lattice.
Karn brings two important abilities to the table. One is a static ability that in combination with Mycosynth Lattice locks your opponent almost completely out of the game – including preventing them from tapping their lands for mana. The other is a -2 loyalty ability that makes sure you actually get your Mycosynth Lattice, as long as the card is in your sideboard.
It's interesting to note that Karn, being the kingmaker that Mycosynth Lattice owes its power to, costs only about a fifth of the artifact. This may still change, of course, when Karn, the Great Creator goes out of print. Any future reprint of Mycosynth Lattice could also create enough supply to meet the demand and reduce the price from its current level of around the 40,00 € for near-mint.