Design the recognition ladder: solution marks, contributor badges, annual awards, moderator roles, speaker slots at your events, early access for top contributors. Publish who is winning.
The investment is nearly zero and the return is a self-sustaining support and content apparatus, compensated in a currency that costs the company nothing and that members value more than money: recognition among peers.
Status must be earned in public
One caution from every mature community: status must be earned in public by verifiable contribution, or it becomes politics and curdles.