Illustration: Naomi Robinson
Since no limitation is specified, you may use this action to build from your hand or directly from the Market.
"Any park" means your park and those of your competitors, so the upgrade being "cast in wax" can be in your own park.
The effect applies to built-in upgrades and non-built-in upgrades alike, including Theme upgrades that are indicated by the built-in theme icon, such as on super attractions.
As with all effects that mention a marked coin price, if a card's price is marked in a different currency, such as Alien Influence, then it doesn't have a marked coin price, and isn't a suitable choice.
The House of Wax is an extra option allowing you to use an action to build an item for a lower price, but it doesn't actually reduce the price of all the other items in the Market for you.
If you used the House of Wax and paid a non-zero amount of coins to build an upgrade, and the upgrade came from the Market, then you can build a second attraction or upgrade from the Market for free using the 2-For-1 Deal if it is the active City event that round.
You don't get to choose a free build up to the marked price of the item, only the amount you actually paid, just like a real-world 2-for-1 deal.