Fuel is a big chunk. Petrol's around $1.50-1.70 per liter lately, diesel similar or a tad higher. For a small-mid car getting 8-10L/100km, the full Sydney-Cairns run burns about 250-350 liters. That puts fuel at $400-600 total. Split two ways $200-300 each. Prices drop a bit in regional areas but spike in cities or remote spots. Tip: fill up in bigger towns, drive efficient (no speeding), use apps to find cheap stations. If renting a campervan or bigger vehicle, add 20-50% more.

Vehicle rental if you're not bringing your own. Economy/small car $30-60/day average, but for longer trips with unlimited km deals it's often $40-50/day. For 14-20 days that's $600-1,200 total, plus one-way fee if dropping off in Cairns (can be $200-500 extra). Campervan/van rental jumps to $80-150/day in peak season, but includes sleeping so saves on lodging. Insurance add-on another $10-20/day. Value tip: book early, compare sites like East Coast Car Rentals or bigger names, go manual transmission for cheaper rates.

Accommodation varies hugely. Camping or holiday parks $30-60/night for powered site (great for couples/groups, includes showers/BBQs). Hostels dorms $25-50/night per person in popular spots like Byron or Noosa, private rooms $80-150. Motels/Airbnbs $100-200/night for two. For 13-20 nights, camping heavy could be $400-800 total for two ($200-400 each), hostels/mix $600-1,200 each. Stretch dollars: camp most nights (national parks like Noosa or Cape Trib), book hostels off-peak, use apps for last-minute deals, or wild camp where allowed (check rules, some beaches ok).

Food can be budget or blowout. Groceries for self-catering (BBQ meats, pasta, fruit) $80-120/week per person if cooking often. Eating out: café brekkie $15-25, lunch fish/chips or takeaway $12-20, dinner pub meal or seafood $20-35. Figure $50-80/day per person if mixing, $30-50 if mostly cooking/picnics. For two weeks $500-1,000 each. Save big: shop at Coles/Woolies, hit markets for fresh produce, BYO alcohol to campsites, limit fancy restaurants.

Attractions and extras mostly free or low-cost. Beaches, national park walks, viewpoints all free. Wildlife spots like Currumbin Sanctuary or koala hospitals $20-50 entry. Great Barrier Reef snorkel/day trip $150-250 (big one, worth budgeting for). Fraser Island 4WD tour or permit $100-300 if doing it. Skydiving, whale watching, etc. add up quick. Figure $300-800 total per person for paid stuff. Tip: stick to free hikes (Bondi to Coogee, Daintree boardwalks), snorkel from shore where possible, use national park passes if multi-day.

Other costs tolls minimal (mostly free highways), parking occasional $5-15 in cities. Souvenirs, coffee, beers another $100-300. Phone/data $20-40/month.

Rough total per person (solo, mid-budget, 18 days, sharing car/room where possible): $2,000-3,500 including rental/fuel/food/lodging/basic attractions. Couple sharing: $1,500-2,500 each. Super budget (camping, self-catering, minimal paid tours): $1,200-2,000 each possible.

Strategies to stretch your dollars: Go shoulder season (March-May or Sept-Nov) for lower rates and fewer crowds. Cook most meals, camp 50-70% of nights. Skip some big-ticket items or share tours. Drive steady to save fuel. Use free campsites or low-cost holiday parks. The East Coast shines with free stuff, beaches, sunsets, wildlife spotting from the road.

It's pricey compared to some places, but the payoff is huge, reef, rainforest, surf, koalas all in one drive. Plan ahead, track spending, but don't skip the experiences that make it special. You got this, hit the Pacific Highway and let the adventure roll. Safe travels out their, mate!