"I am on-call about 10 days per quarter, usually 3 shifts of 3-4 days each. I am paid extra for my on-call (after-hours) work, but not at my full hourly salary because I only work when there are problems after hours (e.g. on weekends or late at night.)".
Note that depending on the exact team, Software Engineers at Google may also be part of an on-call rotation.
When allocated 100% to cash (vs. vacation) oncall pay amounts to more than an extra full paycheck every quarter.
If you don't notice an extra $10,000/year post-tax then please, send some of your moneybags to someone who appreciates the value of a dollar. Like me.
For me it's (off the top of my head) about 10%. Definitely noticeable.