Oh this thread is a balm, I'm so there with you.
We also are paying for live-in care, through an agency, at an eye-watering cost and yet I find myself every day having to do something (from the little stuff like sort out the grocery order, order continence products, fix something that's broken, chase OT, research treatments to the bigger stuff like accompanying her to appointments, going and visiting care homes that she's never going to go to).
And although it might only be 10 minutes here and there but it all adds up and distracts me from work and stops me progressing just at the point i should be throwing myself back into work after years of various derailments. And as you say I'm not even her day-to-day carer and despite the cost I'm beyond grateful that someone else is looking after.
And the expense on top of the cost of carers. My mother was adamant that she wanted to go into a care home so we didn't want to buy a new TV, new mattress, an expensive ramp, but as soon as my dad died, she decided that she wasn't in such a hurry after all. And we just don't know how much to invest in the house but if we don't she tells everyone that her children are too mean to buy her a new TV.
The carers seem to love spending money too - only the most expensive Dyson was suitable.
The house is in a very sought-after family orientated bit of an expensive city yet my mother is convinced that every old person addition 'will add value' - as if the 30 something tech-bro who buys it will be paying a premium for the lift, the grab rails, the adapted toilet etc, etc.