Dazzler,
My $0.02: It can be cheaper, depending on what you buy.
I used to commute in Bris on a VTR1000F. Fantastic fun bike, but had worse fuel economy than the 4cyl Charade we had at the time, and chewed rear tyres like nobody's business. It was our all-purpose bike though, if you wanted a dedicated commuter then a dual-sport/motard would be cheap and easy to use in town. If you want to use it on the weekends though, then you're prob going to need to compromise. It will increase your running costs as well if you're buying more fuel and expensive sticky tyres.
I have ridden the big Triumph to work, but its pretty long and heavy and can be a handful. A K-series would be similar, if not longer/heavier. It's certainly possible, but something smaller would be easier in the city.
Parking at work in Bris was $9/day, at the time a car was $13/day. Its gone up since then. Cars got a dedicated spot though, bikes just parked against the walls. Not much of a saving really.
You could park under the overpass nearby for free, but it was always first in best dressed, and there were regular occurrences of bikes being damaged. There were also unwritten rules that would catch out newcomers. IE, no one locked their steering, so that more bikes could get packed in. If you came back early, you'd just move the bikes in front of yours, get yours out, the put the others back. It all worked until a newbie parked in front and locked his steering, buggering up the dozen bikes behind.
As has been said, lane splitting will get you busted in Bris. I was lucky and never got done, but my flatmate would regularly get done for it, poor bugger. He factored it into his running costs.
As has been said, good gear is worth it's weight in gold, and will keep you comfy and alive.
By the time you buy the bike, pay an additional rego and insurance (expensive), and fuel and tyres and servicing and everything else, you're probably not going to be as far ahead as you think (if at all).
But you'll have fun.
Aside - I know a bloke trying to sell a fantastic bike at the moment too. He'd do a good deal for a swagger, I'm sure
It's not a BMW, but its under your budget, and he could probably throw in some of his gear to get you started (so long as you're "tall, lanky bastard" sized). Freight from FNQ to TAS can be arranged easily.
Cheers!
Matto
I don't always Tapatalk, but when I do, I make sure to misspell everything.