That many presents is not healthy behaviour.
The children aren't even opening them all, let alone using and appreciating them.
Buying cheap, disposable tat is a waste of the planet's resources- in manfacturing and disposal costs. The average person in the UK uses 3 times a sustainable level- thank goodness this level isn't normal!
It distorts healthy giving, buying something that you hope someone will appreciate and get joy from using, by just being overwhelming. Will the children learn healthy boundaries on giving?
How is she disposing of the wrapping and packaging? (No Christmas collection here and the tip is always queuing out onto main roads).
Within that budget, she can buy some better lasting quality items that will bring more long term pleasure.
Living with a hoarder is difficult. It's hard to let go and move on. Life is uncomfortable when its constantly obstructed by stuff. Stuff can literally get in the way of positive relationships with other people.
There isn't a "right" amount to give. I give less, but the DCs get their needs met through the year. Last week I had to upsize on pants. They were just given them, some people would save them to wrap- horses for courses.
I look at the toys we already have and what they play with, and how their needs may change through the year, and they don't need much to make them happy. There's also gifts from wider family which adds up. My floors get cluttered enough!
I agree with PPs that there is some emotional issue that she's trying to compensate for.