I really have no experience with finances, considering I'm only 16 years old, but honestly I think that PHP/IOP is a lot more productive in the long run. Inpatient, I think, is beneficial in the short-term, their job is to make sure you're safe, while PHP/IOP is to give you the tools to get through life healthily. Maybe that's why IOP is more expensive for you. For my mom, the hospital for my sister involved copayments as well, but it was obviously less because it was for a week while PHP/IOP was for 3.5 months for me and 2 months for my sister.
What pfrog said is right. Although none of the people will have gone through exactly what you've been through, the feelings of grief and loss and sorrow and pain are universal. The other patients will be able to help you in some way. And hey, you never know. There may be another patient there that has gone through the loss of a child.
Maybe you could consider a grief support group? I lost my dad when I was 11, and it's not the same as losing a son, but my clinician at my program thought that my loss so young was a big factor in my mood problems today. So soon I'm starting at a grief program with other teens that lost loved ones. Maybe you could consider something similar. As far as I'm aware, support groups are free.