I can't help with any ways to reduce cost/members; there are several that come in mind but it would depend on several group- & member-related attributes, which vary a lot, and without knowing any specifics, I'll abstain.
As for a fundraiser or ongoing donation feature, one thing an owner can do is to setup a "operatingfund" gmail account, setup a Paypal "operatingfund" account, link the two, and use it for group donations.? Don't use your own paypal account for this, it's easier to keep things separate, for both tax and usage purposes, otherwise it requires more work to separate the transaction records, etc.? Leave that account there until the need arises.? Then, I first present a concise email to the group membership detailing why donations are asked for, what the features etc are for Option-A (free) vs Option-B (paid) or even maybe Option-C (disband the group), and let the folks decide what they want to do; the Option-B (paid) presented already gives the operating fund address, and you encourage folks to contribute any amount they can, hopefully that can prod more folks to donate.? If after a while the donations are enough for whatever the goal is, fine, if not, I guess you refund the donations and oh well, downgrade the group (or whatever) unless you are willing to front the difference yourself.? You can then keep or get rid the operating fund accounts, up to you.
Yes, it does take a bit of time to manage this as you become the fund custodian; unfortunately from what I've read, the Stripe integration is a PITA, it seems is more oriented to Enterprise groups; I wonder why Paypal hasn't also been added as an option.?
Cheers,
Christos
Christos Psarras