Some truly barmy things happened during the mining boom, especially in Western Australia.

The construction phase for those massive onshore and offshore projects worked like giant sinkholes, sucking in workers from across the nation and around the region.

Salaries on offer were simply gobsmacking.

For example, a pipe welder on a Chevron-led offshore LNG project six years ago could earn $425,000 as a fly-in, fly-out worker.

After I had written about these folk in the context of a projected 33,000 skilled worker shortage for the WA resources sector, one of them rang me up from his home near Margaret River.

He was a bit miffed that my story hadn't mentioned that poor buggers like him had to pay so much tax.

I ventured the observation that he was being paid more than the Prime Minister.

"Yeah, but I bet he doesn't pay 48 per cent tax," the 30-year-old shot back.

I didn't have the heart to tell him that the PM at that time was a she and that like anyone earning over $180,000, Julia Gillard paid 45c in the dollar marginal tax plus a 1.5c Medicare levy.

Many 457 visas issued due to mining boom

FIFO workers waiting at Perth airport in 2013. ( ABC: Fleur Bainger )

But salaries thrown at skilled workers such as this fellow had an effect beyond the Pilbara dustbowl and the isolation of Barrow Island.

There were signs of it at airports around the country, with people in fluoro massing for direct flights to Karratha for their fortnight FIFO stint.

It particularly hollowed out Perth's economy. Public servants left their modest wage jobs and chased the big bucks up north. School-leavers who postponed further education could land six-figure salaries within weeks of discarding their student uniforms.

And the non-mining sector struggled to retain staff. At one stage, a big name restaurant chain was offering a $140,000-plus salary, plus a house and car for people willing to work as store managers in a Pilbara town.

It was trickle-down economics for pay cheques, from pipe-welders at one end and burger flippers at the other.

This is important background when you consider the politicking over 457 visas this week.

Prime Minister Malcolm Turnbull told us mid-week that 457s had lost their credibility and that the Labor Party had been "Olympic champions" on this front.

"Bill Shorten, the gold medal-winner among them all. During his time the number of 457s increased by two-thirds, during the last term of the Labor government," the PM said.

"And less than 10 per cent of that increase went to the mining sector. So, this wasn't about the mining boom and the need to bring in new skilled workers. These were people, working as labourers, working flipping burgers."

The fact that many 457 visas were issued as a result of the vacancies caused by the mining boom sinkhole out West is an inconvenience to this argument.

Worker shortage without 457s

The iron ore hub of Port Hedland, in the Pilbara dustbowl, where many FIFOs worked. ( Supplied: Camilo Blanco )

But when it comes to 457 Visas, the politics has always been cheap. The visa category has been serially traduced by both sides of politics over the years, as well the unions.

However, without foreign workers, Australia would've experienced a considerable worker shortage during the construction phase of the mining boom.

Not just because of the resource industry needing them (there were 6,630 applications for 457 visas in 2011-12, compared to just 230 this financial year) but because of the gaps that emerged elsewhere in the economy as FIFO ate into the regular workforce.

And 457s have proven to be a useful migration stream for valuable would-be citizens; a self-selecting bunch of motivated and largely skilled and educated workers.

This is not to say that the 457 visa regime couldn't have been tightened. The exigencies of the mining boom widened the door for potential abuse and the door has been slow to narrow.

But foreign expertise is still needed, even if employers should be better tested on why someone from overseas is preferable than a local worker.

Which is why Mr Turnbull's abolition of 457s came lockstep with the creation of two other, albeit stricter classes of skilled worker visas.

It might have been neat and nifty politics but it showed once again how economic policy must navigate the easily provoked breezes of xenophobia.