I understand the desire to avoid paying tax by taking cash, but is it common that a tradesperson is paying 50% income tax? I only have a US resident's perspective, but that rate seems very high.
Most trades in Canada are max tax rate, because the max tax rate kicks in at extremely low levels compared to USA.
Someone earning 60K USD in Canada (~75K CAD) would have a marginal income tax rate ranging from 27% to 38%, depending on their province. If they're a contractor, they'd have access to a bunch of deductions against their expenses. They could further use an RRSP to shelter their income, or at least defer taxes to future years with lower income, thus driving their average tax rate down.
So a (filing single) contractor making 160,000 in California would pay more like $60k in total taxes (which is still 37.5% effective).
But given the number of UK folks for this topic, the “Social Security” and FICA amount (~15%, so nearly half of “tax”) is effectively similar to National Insurance.