On the subject of BPA...all plastics will leach some, pretty much, but it only becomes an issue when the plastic is heated. Cool plastic won't leach chemicals...so unless you leave the bottle in the sun for solar still reasons, it's not a real concern.
as for my budget kit...When I go out innawoods, I take my hammock, but instead of taking a $200 tarp, I take a $2 painters drop cloth and a $3 roll of duct tape...if I NEED to, I can rig up a stable waterproof shelter. (in fact, if need be I could use that drop cloth for many many years of waterproof shelter under some thatch).
My sharps kit is my mora (12 or so usd when I bought it) my cold steel kukri machete, and or cold steel military shovel. I always carry a pocket chain saw. (real teeth type, and wire...wire is for bone saw, in medical kit, NOT for cutting wood).
It all really depends on where I'm going and how long I'll be out. The biggest way to save money long term is on consumables. If I did enough winter/rain camping I would definitely upgrade my tarp because the packing and re-packing of the flimsy plastic makes it not last for very many trips, where a good waterproof tarp will last for a decade.
I buy the best quality for the lowest price I can find for gear. All but one of my water containers are steel. Fuck plastic. The weight difference is minute and the durability and multipurpose nature of the material makes it an obvious choice.
The only water container I carry that is not metal is my hydration bladder. It's a $20 or so platypus 2l softbottle, and they are fucking amazingly handy. Solar shower, SODIS, and just transporting enough drinking water for a couple of days without worrying about it, all handy innawoods.
For firestarter I carry these three inch long, pencil thin prayer candles that I find in local indian inport shops. A pack of about 100 runs under $3, and they each have a twenty minute burn time. One candle properly used can provide up to ten sure fires.
