I'll repeat a couple of comments I made recently on this subject on other topics.
My wife's folks are knocking on a bit now and they have the odd health issue as older folks do. She (we) tips up a few bob now and again as and when if they need something as any of us would do with our parents.
It's very definitely a cultural thing. As parents get older, you become the decision making man of the family (or consultant at least). It's a responsibility you take on and perform with solemnity. It's a role that also gets you much respect in the family. We have all heard the phrase "the serious man" haven't we?
Older folk in Russia tend not to cost very much assuming they dont need long term care or anything out of the ordinary. Wifey's folks have a local card she funds and they use if they happen to run low on cash for something or other. As it goes, they very seldom use it and when they do the amounts seem quite modest.
When she is in Russia she is always sure to make sure the freezers and petrol tanks are full and there are no outstanding bills before she goes. But again, this isn't much money.
Now and again they have an exceptional expense, FIL had a knee operation last year and MIL has an eye operation soon. This stuff tends to cost a couple of hundred here and there every now and again.
In comparison to the cost of living in the UK, these sums are occasional and minor. If you can afford to import a foreign woman, minor expenses such as these shouldn't trouble you. She has a responsibility for her parents. When you married her, they became your family too, so you also married that responsibility. With us, and most folks we know, it tends not to be too onerous.
It may be different for those who appear to have inherited a large extended family who all seem impecunious and have a crisis every week, but that is more to do with opportunism on their part and naivety on yours. Sensible people would have established the landscape in this regard before they got married.