My SIL has short arms and long pockets.
She expects fancy handbags, perfume etc - she literally gives DH the exact item. The cost is usually around £70.
We usually give her husband a £25 amazon voucher .
In return, I generally get a cheap necklace - maybe a tenner max, and DH invariably gets a shirt or a jumper. Last year it was a jumper - he hated it and took it straight back to the store, where they gave him a £5 voucher because it was on sale last year.
So cost of gifts to DSIL and DH - £100. Costs to us - about £20. DH says its fine because we can afford it, and they buy for the kids. They go on 4-5 holidays a year, double income, no kids
They also like to make jolly plans like a week away at centre parks for MIL and all of us - they will share with MIL and we are expected to contribute. We need a huge place for our brood. And I can think of nothing worse.
And Mothers day, she wants to take MIL to a spa, which we have to contribute to - it ends up with us paying and her taking the credit.
I've confronted DH and pointed out how unfair it is, but he justifies it - to himself. I no longer get involved. No more thoughtful gifts, I leave it up to him.