Mortgage insurance is proportional to your LVR and there's a law of diminishing returns to it, which starts to get awfully shitty when borrowing at high LVRs.
Here's a good example - you have 70k saved up as a first home buyer, it could be allocated as such:
A. 600k property, 5% deposit of 30k, LMI of 26k, stamp duty 15k = initial upfront of ~70k and your LVR is 95% on 570k borrowed
B. 500k property, 10% deposit of 50k, LMI of 9k, stamp duty 11k = initial upfront of ~71k and your LVR is 90% on 450k borrowed
So whilst 100k difference between the purchase price of the two places, the more expensive one actually requires you to borrow 120k more due to money spent on LMI (and some for the extra stamp duty).
One loophole you could use to avoid this - get a relative to borrow and "gift" you enough to make up a 20% deposit and cover the stamp duty - you finance the other 80% = no mortgage insurance and you just service both loans. Or they can go guarantor on the loan and you technically don't need any deposit or LMI.