My Mom and I were just discussing this - and some of the ideas/suggestions we bounced off each other included but were not limited to:
Purging old accounts that are taking up server space. People that have not touched SL in ten years are probably not coming back. And even if they do, nothing in their inventories would be relevant - so you send an email to the email address on file and give them to the end of the year to log into their account if they want to keep it. If not - purge. Same goes for land/parcels that have not been touched. Tons of "abandoned land" just sitting - taking up server space.
Offer tiered Premium subscriptions. Something like a $5/mo option where you only get the perks of getting into events easier - some people definitely have it ONLY for this. It would include no parcel, no extra groups, and no stipend. Then go from there. Next step up gets more groups, small stipend, land/house. Next up gets even more groups, bigger stipend, etc.
ASK the community what they would like to see as options. "We need to raise the prices for the first time in x amount of years - here are some options we came up with. We can either take away THAT and give you THIS..or..." INVOLVE the people that are playing! WE are the ones this affects!