Mad money in the sense that he is 31 and his game relies on a pace/trickery. You could get a year or two out him but I would be amazed if he doesn't decline soon.I'm not sure it is mad money any more. Especially as he's consistently their highest scorer by some distance (last year he scored and assisted more than Diaz, Gakpo and Jota combined) and still one of the top 10 in world football.
I think it's easy to look at £200m as transformative, but if losing him means that Liverpool don't qualify for the Champions League this season, then they'll likely be more than £200m down across the next two seasons, and may be locked out for longer.
Arsenal had £50m higher revenues than Liverpool in 2016/17 when they failed to qualify for the Champions League. Five seasons later and their revenues in just one season were well over £200m lower.
If they were in the CL this season, and didn't have other problems in the squad, then they'd be more confident, but I can see why they would think even £200m is a risk.
Your point about revenue is excellent. Liverpool owners are getting away with murder. They are not as bad as the crooks at Old Trafford but they are not far behind.