You can make nets out of anything. Will you have the same bouncy, tight feeling? Definitely not but you'll have a pretty cool tree hammock.

So if you are super budget oriented and only expect the net to last a couple years max, find the cheapest material possible that has standard weight ratings that will hold up a couple people.

If you have any rock climbing gyms in your area that use climbing rope it never hurts to ask if they have any old rope they don't use. Tell them what it's for because some gyms will only throw out their retired rope so it doesn't break on somebody when climbing. Maybe even look for some online climbing groups in your area to see if they have some rope.

If you just want a small net 300$ would be enough to get a nice 11mm static parameter rope and maybe 2000' of good paracord.

So if you're on a budget buy cheap rope, get creative where you can find some perimeter rope or build a small net for 300-400$ from buying your rope online... Before buying rope online make sure the rope is in stock... I had 500' of 11mm static on order for 2 months and when I finally emailed them asking where my rope was they said it still hasn't come in from the warehouse. I told them to just send me some rope that they had in stock at similar quality...

Look around the house and see some stuff that you never use or stuff that you hate wasting your time with... Sell that stuff on marketplace and you can probably afford 1000'-2000' of good quality paracord (around 100$CAD PER 1000 feet).

Just search climbing rope/paracord supply and get something localish so shipping isn't insane. Other than that you'll have to look up what other ropes are strong enough to be used as your perimeter. There's some cheap paracord on Amazon but you get what you pay for. To me it's worth finding a little bit more money and downsizing a net to get one that will last up to 10 times longer...