> I haven't seen one (at least for a SaaS company) that will compensate for loss of productivity/revenue
They won't show up on automated systems aimed at SMEs, but anybody taking out an "enterprise plan" with tailored pricing from a SaaS, will likely ask for tailored SLA conditions too (or rather should ask for them).
It's hard to give a compensation for profit loss, as then you would have to know the profit of the customer beforehand and put an adequate pricing including that risk. It's almost like insurance!
Granted, there's probably not many businesses that are losing major revenue because slack's down for half an hour, but it's nice to at least see them acknowledge that 1 minute down deserves more than 1 minute of refunds!
[0] https://slack.com/terms/service-level-agreement