If you're lucky you'll get to LAX for 1100.
However, this is during Christmas/Holiday season, you won't get it for that cheap (most likely). It's probably going to be 1500+.
Booking directly to NYC will very likely outprice going domestically. That same flight you're paying an extra $500 for to get to NYC and back is the same one I buy last minute through a domestic source which they flag as "graveyard / nonpeak flights" and they are RIDICULOUSLY cheap (this is literally how zxv and I got to SKTAR2 last year, I'm pretty sure we got one way flights over for like $100 each, pissing off many of my Amerifriends). Domestic hopping throughout the US is very cheap if you have the time, patience and will (for awkward times/waiting periods). I've bused a fair circumference of the US for a total likely less than $100.
Depending on your length of stay and who and how you know people you can get away with cheap. If you have no standards in eating (fast food in Australia is a standard higher than the US, sorry), you can be free flying at probably $10 a day for food. Otherwise good/healthy options are around the same price as here (well, cheaper there actually, organic produce/etc is more mainstream and is about the same price as we pay for otherwise in Australia).
Housing can sometimes be hard, especially in the NYC area. And by hard, I would say pretty improbable. Depending on your length of stay you should try base yourself in places with more readily available lovely housing smashers and find your way over there. Worst case scenario during the tournament will be sharing a hotel floor for like $5 or $10.
Any really super safe budget would be $X to LA + $500 to move around within the USA + $100 a day.
I'll hopefully be in the US during the time basing in LA.