OK basic survival kit necessities include:
shelter from animals and elements, first aid, food acquisition and prep, potable water, fire, self defense, signaling,
maintenance of all of the above
Packs are like handguns or bike saddles, you have to try them on before you buy as they are all designed differently and fit differently on different people. Kelty's military packs are the bomb. Very adjustable, very rugged, very high quality with MOLLE strapping for mounting custom pouches and sheaths. I think the ideal pack is an Eberle or a Mystery Ranch Kodiak but these are both out of your price range, and when I think "survival kit" I think squeeze everything you can into an 80-90 pound pack because you don't know what is going to happen. Maxpedition and Tactical Tailor also makes good bags.
Pack-100$
Camelback or Blackhawk 3 liter water bag-20-30 dollars
Used Leatherman Blast on ebay-10 dollars
Kabar Warthog Folder-14 dollars
9x12 1 mil thick plastic painting dropcloth-5 dollars, for uses see the poncho thread
Ketadyn filtered water bottle-20 dollars
Slumberjack Solara sleeping bag-30 dollars
strike anywhere matches dipped in candlewax kept in match safe-10 dollars
flint rod-3 dollars
Hatchet-Gransfors is sex but brand and price range is up to you
Ontario Camp Machete-10 dollars
Smith's 2 stone/oil honing kit (gotta keep that 1095 rust free)-15 dollars
Hiker's first aid kit-10 dollars
lip balm-2 dollars
small jar petrol jelly-2 dollars
cheap saucepan-5 dollars
suunto compass-15 dollars
map of general area-10 dollars
generic daily vitamin supplement-5 dollars
.75 inch fishnet-5 dollars
survival blanket-2 dollars (shelter construction, signalling)
Small fishing kit with line, jig heads, sinkers, spinners-20.00
spool of 160 ft GI tripwire-2 dollars
Air Force SERE field manual-5 dollars
notebook and pencil-negligible
Darner needle-negligible
550 chord, 300 feet-negligible
Duct tape-negligible
Toilet paper-negligible (kindling, clotting material for gaping wounds...)
A brain that works and a will to live-priceless
now you have fire source and tinder
water storage
rough use cutting tools for shelter construction, self defense and general utility
sharpening kit for maintenance of tools
multitool and utility folder for general utility
snare wire, fishing kit, SERE vegetation guide for food acquisition
sleeping bag for protection from the elements
filtered water bottle and saucepan for potable water
saucepan for preparation of food
necessary first aid
sewing materials for cloth maintenance
blah blah blah i've rambled on too long, you see where I am going. Compress everything in ziploc bags for water and rot protection. Should give you a good head start on a 500 dollar survival kit. Like I said, your reasoning skills, knowledge of fieldcraft and a will to survive are the key essential things you need in a shit hits the fan pack. I squeeze all this stuff in a Eberle Operator pack with a Ruger target grey frontier in .243, ammo and caliber specific cleaning kit, and it weighs in between 70 and 80 pounds based on the extra clothing and area specific requirements. I ditch the rifle for day to day hiking but for the most part its what I carry hiking on a daily basis.
