I was thinking that if I used older equipment that I have, I would just use the price I paid, whether it was new or used at the time. For example, I bought a used cube from someone on here for $50 years ago, and if I decided to use it for my build, I would take away $50 from my budget. I also feel like the $500 should be somewhat of a soft cap, like you can go over, maybe up to $1000, but you lose some “points” based on how much you go over. Gives more flexibility, while also encouraging more bare bones setups.
The way I envisioned this contest was a “destruction derby” of sorts, or like how my neighbor ran a contest where his club would invest our same budget of $500 into a car and race them lol.
Even though getting good deals on equipment will give you an upper hand, I feel like better results with a more basic setup should be the goal.
Maybe the numbers/rules could be tweaked a bit? Like lower budget, but only equipment goes towards the budget, livestock is unlimited? Whether you have a green stripey mushroom or an OG bounce mushroom, I feel like they are going to grow relatively the same, the difference will come down to equipment/husbandry skills, which I feel like is the goal. As long as you are doing things right, anyone can grow coral/grow it well, even with basic equipment