In some cases it is reasonable to expect more. But, if other people are offering the same obvious solution for $25, then $25 is a reasonable reward, regardless of how much it saves the company. In which case expecting more than $25 is greedy.

I think the $5000/month example is likely a very rare event. Perhaps the management did compensate that particular employee separately without telling everyone else.

My point is, if a company sets a policy of pizza party and spin the wheel as a reward, that's the reward. Don't complain after the fact that it's not fair. You didn't have to submit the idea, you could have gone about your business and never said anything. Also, what if 99% of the idea's only save the company $20 or less? You really think they are going to start writing $2 cheques? Or is that even going to motivate people to submit ideas. Pizza parties not only reward the employee, they provide a morale booster.

More likely the manager used the $5000 per month saving idea to promote himself for a raise than pass on compensation to the employee