We used one for our first child. Went to the hospital in the evening, long night of laboring, eventually got an unplanned c-section like 12 exhausting hours later, and then a couple days in the hospital.
Doula was very, very helpful in this scenario. Basically a 3rd person on hand so it wasn't just me (fairly useless beyond chores/tasks) and various nurses coming to poke and prod. Helped my wife understand each step of the process, advocate for various things in the way that the nurses understood, etc. And then a 3rd set of hands to help with everything for ~12 hours after the c-section at which point everyone's terribly sleep deprived and there's still an onslaught of new information, etc...
Absolute most helpful part was helping my wife during contractions and other times where she's basically going wild with pain and her body is doing things it's never done... and having someone who can hold her hand, massage her back, and lead her through breathing exercises while it's all happening was just extremely helpful.
If you had a midwife on hand that'd probably be just as good. The important difference is whether they're basically with the hospital, or with you. If they're with you they advocate for you and have done this 100+ times so they're well versed in everything. Or if a mother/mother-in-law is much loved and happy to help and won't drive you crazy in the hospital room.
Second kiddo was a planned c-section, no need for a doula.
I think we paid ~$800 all in all, including some pre-hospital visits for exercises and other helpful tips for pre-birth physical therapy and other preparations.
Also I think insurance may have covered 100% of it... or at least half. Basically it's categorized as pregnancy-related healthcare. Hospital was all fine with having the doula on site.
Doulas can also be fairly woo-woo... spiritual birth, earth-mother yadda yadaa... if you want that, great! But ours was very straightforward, like a midwife/nurse but without the medical qualifications. Basically an experienced carer/guide, not doctor/nurse.
Enough rambling! See if insurance will cover it. I think Doula-Connect dot com is a site that matches you with local providers