My daughter no longer does GS, but she joined in 4th grade as a junior. We live in a small town, and all our troops, Daisy through Seniors meet at the same place and time. We merge together for large activities like Thinking Day, Juliette's Birthday, etc. Also, during cookie sales, one of the leaders creates a spreadsheet with all the booths, and sign up genius, so girls can sign up for various dates and times. Then, they use a formula to allocate proceeds to each troop, based on how many hours of booths, Daisies, for instance, participated in. I'm hoping you can do something similar with the older troops in your area. You can save expenses, because our older troops pass down the girls and leaders books.
Also, if you're running a meeting, and need pipe cleaners, or construction paper, or whatever, and you forgot it, it's easy to ask one of the other troops for a loan. I always had a large bin of arts and craft supplies, and the other leaders did as well, so we could share.
Back to your original question, each family pays dues. The dues aren't even to the troop, it goes to national. It used to be $18, but sure it's gone up. Also, each girl purchases vest, troop numbers, and American flag. If you're getting push back from parents, basically they have 2 choices. They can pay for all the badges, activities, etc themselves. Or they can really step up, and help the kids sell the heck out of Fall Fundraiser and cookies. Fall Fundraiser always got a higher percent of the $$ going right back to the troop, as opposed to cookies.
Finally, you will absolutely need lots of help with cookies. The girls can create really cute posters at meetings. Then you order as many cookies as you think you can sell. But someone has to set up the table, you need at least 2 adults to be in charge of money, and they need to reconcile the inventory to the $$. Someone needs to haul the cookies to/from the booth. We did 2 hr shifts outside grocery stores, Walgreens, etc.
This first year, maybe the girls just sell the cookies to neighbors/friends/family. I'll tell you, even with all the help from other leaders, the cookies were a lot for me to handle. If one of my parents flaked out, I felt responsible to come cover their shift at the booth.