Devops contract rate seems to be around £450/day (at the low end). Assuming 21 days per month and 2 months off per year, you'd be looking at £94500 revenue. As a contractor you could expect to pay as little as 25% total tax, but if we assume 30% you're looking at taking home £5.5k per month. Which is a grand more than an £80k salary (with an extra month off).

If you're married and have your SO as a shareholder, thus splitting the tax load you can almost match a £200k salary on a day rate of ~£700 (I have seen a few devops type roles getting up towards that figure).

So, I agree that £250k salary is very top end, but there are certainly contracts in the finance industry that pay enough to get you close if you change the way you're paid.