Who pays for the baby shower?

Okay, so I need opinions. My MIL and SIL took it upon themselves to host my baby shower. I didn’t ask them, they just made themselves in charge. I didn’t have the heart to tell them no. But the last time my SIL was my maid of honor, she didn’t do ANYTHING. So the last thing I wanted was her help again. Well now it’s at the end of the month and they haven’t helped with anything. They then said “you can start buying decor, food, tables/chairs etc.” and we will put everything up the day of. So it went from them planning it, to me planning it AND paying for it. My question is: who is supposed to pay for the baby shower? I was always told the host. I’m so frustrated because I wouldn’t have had them in the first place, and now I’m stuck and have to pay $400 myself. Please help :(