The better office chairs have 10+ year warranties, if you spread out the cost of buying a cheap chair (£150) every 2 years Vs a £1000 one that lasts 10 years its not such a huge difference in price whilst the benefits to your back are worth much more.
I know not everyone can afford this, but it’s worth checking for interest free credit from either the manufacturer, store, or even PayPal / klarna (which is what I did).
I WFH, so my chair gets a lot of use - it’s one of the tools I use.
If I was an electrician, or I commuted to work I know I’d be paying for tools, fuel, repairs, train tickets etc
I don’t know what your circumstances are, but I find a cheap chair falls apart pretty quick.