Please do not pay attention to the last post by the noob. His adverse statement of a necessary $40k-$50k budget is absolutely ludicrous. (NEUB)
Like Pecha72 has said above me, in my travel experience I have earmarked budgets per time spent in local regions. I.E. Alaska/Canada is more expensive then the mainland US, which is more expensive than Mexico, which is is more expensive then Central America, so on and so forth. More time spent in expensive places = higher daily budget and vice versa.
Dig deep and get into the research as much as possible. Obviously you are well over a year away from your stated departure date (which you moved back a bit already?) and thus have time to read and read and read. Temps in February in Melbourne are generaly higher than 75F. Thats the end of summer here in Australia. But that's irrelevant.
Camp your ass off, and you'll keep your costs low. Buy your food at grocery stores and markets, and never pay for a cooked meal, and you'll keep your costs low. Sleep in new friends homes, on floors, couches, etc, and you'll keep your costs down. Things you can't change are A) the price of fuel, B) The cost of food C) Weather.
Fuel in Australia is around $1.40/liter at the moment. i.e $5.35/gallon. Turkey= $10/gallon. I've got no idea about Indonesia, any parts of Asia, or the rest of Europe, but you can plan on damn near doubling your fuel costs in Europe as compared to the US. Food is expensive in many places, cheap in others. Save when you can, spend when you have to. Weather, like it or not, will impact your travel plans, planned destinations for the days travel, likelyhood of camping (pissing rain somewhere in Asia? 100*F heat in Australia).
Your bike will get around 55-60mpg (don't be optomistic about fuel consumption, plan for the worst man, it will save you time and money). You'll be loaded with gear even though you'll travel lightly. If you do 290kms (call it 300km or 180miles) a day, you're burning 3 gallons of gas at 60mpg. $16/day in Australia. $30/day in Turkey. Trying to feed yourself and cover misc. things on $24/day in Australia will be tough as nails. Nigh impossible on $10/day in Turkey. IF you can find a free place to sleep.... maybel you'll be inside your budget...
Shipping your bike to Australia will cost you more than you expect. Shipping from the west coast of the US to Sydney/Melbourne/Adelaide/Perth (doesn't really matter) will cost you roughly $600-$1000 JUST TO LEAVE THE US. Wharf fees, Customs fees, AQIS (Australian Quarintine) Fees, Cleaning fees will cost you another $1000+- on the Australian side. You can do it cheaper, but time is your enemy, you might have to wait a few months for the right shipment to leave the states that can add your bike for cheap, and save you money. How do I know? I manage an Australian based import company that imports US boats/campers/motorcycles, etc. So, roughly $1500 to get your bike to Australia. $1200 for a one way ticket from the east coast. You're at $2500 already. I don't know what the rest of your flights will cost ($400-$500?) or the ferries. You'll have to figure that out.
Do your research on the Carnet, it'll easily cost you a thousand dollars ($1,000). You've got a cheap bike, which will lower the deposit required, but it's still not cheap.
Your border fees estimate is probably pretty close. Australia won't cost you any money, but I'm not sure about the rest. You won't be paying much in Europe, but the "Stans", Russia, Georgia, Turkey, will stick you for some bucks to be certain. Your map shows you entering Pakistan? Did you find an easy way to get a Pakistani visa? If so, tell me, I want to know (for real, I want to know).
If you don't crash, you won't have much repairing to do to your DR350. Very reliable, air cooled, bikes. Start with a clean, well prepared bike, and you'll end with a well used, still in good shape, well prepared bike. However, you're planning on over 26k miles. That's a LEAST 3, probably 4 rear tires. And at LEAST 3 front tires. You'll be paying $100 for each of those 6 tires (AT LEAST). You'll have 8 oil changes at 3k mile intervals. 4 oil filters if you skimp and only switch every other. You'll have to buy a chain half way through, or near the end at least. That's an easy $1000 all said; tires, oil, filters, chain. Probably closer to $1,500 in all honesty.
Lets add it up:
26k mile at 60mpg = 433gallons x $5/gl avg= $2,156 (really, it'll be more like $2,700) (http://www.kshitij.com/research/petrol.shtml
Food for 150 days = $17/day (you gotta eat man and Australia/Europe ain't Cheap. You can't stay in India forever!) = $2550
Consumable parts / Maintenance = 4 rear tires, 3 front tires, a chain, 16 quarts of oil, 4 filters, and other miscellaneous expenses =$1,200 (DON'T CRASH!)
Carnet = $1500
Shipping to Aus with one way plane ticket = $2500 (likely won't be cheaper).
Border fees = $1500 (have you included your visa fees also? Pakistan, Russia, the other Stans, Turkey, etc.)
Other shipping costs $6500. (as per your estimate)
Where are we now? Oh. $17,900.
It seems like you've landed pretty well on the mark. You might even come out under this proposed budget if you save on shipping costs/flights. However, this does not lead ANY room in the budget for incidentals or tourist activities, or alcohol, or meals out with friends. This doesn't cover any new clothing on the trip. Replacement costs for any items lost or stolen. What if your camera breaks dude. You will definitely want a new one. You haven't taken into consideration your motorcycle gear either. Boots, Pants, Jacket, Gloves Helmet. ATGATT. All the gear all the time. Is that in your budget, or is that a pre trip expense not to be considered for these purposes? Your new to you DR350 will make the trip without a hassle. Buy a 4gallon Clarke tank, hand guards, a new seat, and some throw over soft luggage, and you'll be fine.
I rode 8 months, from Seattle to Argentina. My average was 100mile a day WHEN I was riding. 160km/day. Your average of 290km/day is going to kick your ass and take your name (unless your ruthless, in which case it won't matter at all). Remember, you can sit in India somewhere for a week and spend less than $70 and ride nowhere at all. That same week in Australia will cost you $500+ Are you on a strict timeframe? If not, why not travel until the money runs out instead? I'd be looking at 7 months time.
In fact, I am planning 9-12 months for the same journey. Australia to Europe. After 3 months in Australia ramming around. And another 3 months to descend into Africa (if I feel like it).
Hauling ass costs more money. The slower you go, the cheaper it is.