Although the states get most of their money from Canberra, the NSW government still collects some revenue including mineral royalties, payroll tax, land tax and transfer duties.

The budget papers say falling property prices and flat wages have led to "substantially lower tax collections" for the state, offset by higher coal royalties "in response to an improvement in international competiveness, via a lower currency and wages".

With higher than expected thermal coal prices and a lower exchange rate providing a greater $A return on a product sold internationally in $US, mineral royalties are predicted to hit a peak of $2.074 million this financial year, before dipping slightly to predictions of above $1.95 billion for the coming four years of estimates.

To put these amounts in perspective, this year's predicted $2 billion-plus figure is more than $300 million more than the 2017-18 take of $1.76 billion.

Previous figures were $1.58 billion in 2016-17, $1.19 billion in 2015-16, $1.25 billion in 2014-15, $1.34 billion in 2013-14 and $1.31 billion in 2012-13.

Elsewhere, the budget papers reveal sharp increases in debt, with general government sector borrowings rising from $37 billion this year to an estimated $73 billion in 2022-23. The interest bill is about $2.8 billion a year. The net debt figure goes from minus $8.8 billion this year to $38 billion in 2022-23.

When the railways, water authorities and other government corporations are included, borrowings rise to $104 billion in 2022-23.

NSW Budget a mixed bag for the Hunter