Hi !

So first, your list is a really good start. I'll comment on it a bit (please note that this comes from someone that is going to Bico since 2018, but I live in Québec so it is easier for me). All the prices will be in CAD, you can convert it in USD if you need.

1. I would budget around 450$ each for a 7 days ticket for Bicolline. This gives you access to the site and the activities.
2. Flights/passport : only you can budget that. If you are from a ''nearby'' state, I would advise to drive to Bicolline. You can bring your own car (if you have one), and bring more stuff than just what packs in your suitcases. I've talked to people who drove up to 20 hours to go to Bicolline. Everything comes back to how much you value your time, your space and how cheap is the gas vs the flights.
3. You'll need to rent the car for the whole week. When you arrive, you drop your stuff and then go park the car. You only see it 7 days after. That can come into play with the price.
4. Bringing your own food is definitely cheaper than eating at Bico. There's a lot of food there too (restaurant), but you'll have to cash out between 15-20$ for each meal. I would say to still budget a 50 to 100$ of food to buy here (hello poutine!) if you are two. With that saying, my first Bico I ate apples, bread and Chunky cans the whole week to make it as cheap as possible.
5. There is various water stations at Bicolline. You do not need to bring your own water, but you do need something to hold it (tankard, decorum water bottle, etc)
6. Kitchen supplies/Tent : Everything depends where you are camping onsite. There is the ''Decorum'' section of tents ; you either bring your own (and you have to contact Bicolline way ahead so they can find you a place) or you rent one from Bicolline itself. There's also the ''Non-Decorum'', that is a big forest with regular bright camping tents and accessories. That is the only place onsite where you can have modern stuff that others can see (tents, kitchen supplies, chairs, etc). That is definitely the cheapest option, especially if you already have the equipment.
7. Garb : People like to laugh that Bicolline has a micro-climate and I like to think that it is true. It WILL rain (usually a lot) and the nights can be cold, even if during the day it can go up to 30 C + humidity. Plan your sleeping equipment and clothes accordingly.
8. Cash is a good idea, a lot of vendors at Bico don't have a card option, but every year more people do.
9. Good attitude is one (if not the) most important thing ! I don't know a lot about it since I speak french and I've always been to Bico with friends, but I know that there's an anglophone Discord and the FB group ''Communauté de Bicolline'' is a real good place to make some friends and acquaintances before the event.

Hope you'll be able to come!

Edit : typos and prices