All my family love gift giving. Everyone produces a wish list in October that is circulated and includes everything from small trivial items to more expensive, I do not think anyone has ever got everything on the list and present buyers are free to buy things not on the list if they know it is something that the person will enjoy.
Yes, most of us can buy anything we need, but we tend, as the second half of the year comes round to put things on the list that we would otherwise buy, but are not urgent - books, odd devices, small items for the house.
We do not explicitly set a budget, but the £50 lots of people mention is roughly where we are at, although it can vary a lot. We treat our DiL as a member of the family in everyway, and would never treat her differently from her husband, or their children.
We would never give cash, unless it was to buy a specific item we cannot source, and even then like to see the obtaining and paying happening before Christmas day.