I temper my wardrobe, handbags, and jewelry when I visit DH's family. There's nothing else to be done. It keeps the peace.
My MIL has complained to me that "I have so much! And that her daughter (SIL) has so little." SIL made many ill-advised choices when she was young. She has an Ivy League education and has done little with it. She only dated actors and musicians -- the cool people -- doctors, lawyers, accountants, and professionals were B O R I N G. Her choices led to negative consequences. DH's family bought SIL her condo, paid for her lifestyle, vacations, etc. It was if her parents said to SIL, we don't think you can make it on your own, but here's enough so that you can get by and be dependent on us.
Over time, my relationship with my in-laws has evolved into a equilibrium of sorts. MIL and SIL know that once MIL passes, DH and I will be her only geographically close family.
There was a time when I was jealous that my in-laws paid for my SIL's condo and lifestyle. But then I realized that the struggle to be independent honed me. Working three jobs at the same time, no car, no health insurance, and little parental largesse made me the person I am now. You have to let your kids struggle (as painful as that is to witness) in order for them to grow into successful adults.