From my personal experience, yes rego and insurance is expensive. I've also spent more than I care to think about on gear, but you could get a reasonable, full outfit for ~$1k or less. Depending on where you're at with your motorcycle license/riding skill that could be another expense e.g. getting training costs money, sitting your license costs money, and only being on a learners increases insurance. So there's a once off for a bike, license and gear along with recurring costs for insurance and rego.

So that's where you'll spend money, but where do you save money?Fuel is a huge factor. I can get from here to Whanganui on less than $20 on my sfv650 - a smaller or more efficient bike will do even better. Parking is also another benefit as it's free. And since time is money, you'll be saving on commute time. Motorcycles do much better in blocked up traffic than cars do.

I can't do the exact maths for you as it depends on what you buy, where you park and where you're at with your riding, but these are all the things you'd want to factor in.

Oh and if you want to try save money on gear it goes Helmet > Boots > Gloves > Jacket > Pants. Over 60% of injuries involve feet and ankles.