The price of 1 x cassettes is indeed eye watering, for example I recently paid €95 for a SRAM 11 speed 10 - 42 cassette, an equivalent 9 speed SRAM cassette would be €22. That cassette is certainly one of the cheaper 1X cassettes around and there are many at much more eye watering prices.
To balance that out slightly though is the longevity of these cassettes. People often erroneously think that 1x drive trains wear out more quickly, when in fact the opposite is true. One test was ran by Zero Friction Cycling and their results are mentioned in this article:
https://cyclingtips.com/2019/12/the...ity-and-efficiency-tested/#8-9-10-11-12-speed
"It seems that with each gear added, durability has improved. And at least for Shimano chains, 10-speed saw a significant jump in durability from 9- and 8-speed, and Shimano’s latest 12-speed XTR mountain bike chain rules the roost as Shimano’s most durable offering."
I can certainly attest to that with my own experiences, the cassette on my bike has been on there since 2016 when the bike was manufactured and has certainly not seen the kind of pampering or looking after that it should of done. I don't really tally up my mileage, but it is quite a few thousand, most of which is off-road, along with touring and year round use. The only thing I have done is replace the chain when it reaches a certain amount of wear and I currently have gone through 3 chains in this time. It is almost at the end of it's life now though and I do have a spare sat on my shelf for when it finally dies, but It's still hanging on in there.
Before anyone mentions it, I know this doesn't completely balance out, you would need to buy nearly five 9 speed cassettes for the price of mine, and so 9 speed definitely wins hands down in the value for money stakes. The point I'm making though, is that you will get a lot of mileage out of 1x systems and you won't be having to be regularly dipping into your pocket for new drivetrain components.