Going rate for a nanny is about $25/hour or about $4000-5000/month in the Bay Area, so yes, it was roughly the same price. I know many, many Googler families with daytime nannies, night nannies, multiple nannies, etc.
The two main things you got with the in-house daycare was a.) consistency and b.) convenience. I have a teammate whose kid went through the Google daycare; she said that at the time (over a decade ago now), it really was quite high quality, and because the caretakers were in-house employees of Google, they had passed the same high bar as the rest of Google employees. (I've also heard that this - like many other things about Google - has gone downhill in recent years, and that people whose kids went through post-COVID dealt with high staff turnover and inadequate care.) Meanwhile, almost everybody I know who uses nannies for full-time care has had horror stories about finding a reliable nanny. Some are flakes who don't show up to work; some seem to have perpetual car trouble; some are neglectful; some always have their boyfriend come over and spend more time with him than the kids; some get fired for putting the kids in danger. Nannies are not licensed, unlike daycares. It's very much parent-beware, and a lot of people don't have time to search for a good nanny, hire them, and monitor them to make sure their kids will be safe.
There's also just a convenience benefit from having your kid on-site. You can share commutes; you can use the carpool lane; your schedules are identical; you can pick up your kid in a blink if they get sick; you know they're always close; you don't need to coordinate logistics with a nanny; your time schedules will overlay; and so on.
The two main things you got with the in-house daycare was a.) consistency and b.) convenience. I have a teammate whose kid went through the Google daycare; she said that at the time (over a decade ago now), it really was quite high quality, and because the caretakers were in-house employees of Google, they had passed the same high bar as the rest of Google employees. (I've also heard that this - like many other things about Google - has gone downhill in recent years, and that people whose kids went through post-COVID dealt with high staff turnover and inadequate care.) Meanwhile, almost everybody I know who uses nannies for full-time care has had horror stories about finding a reliable nanny. Some are flakes who don't show up to work; some seem to have perpetual car trouble; some are neglectful; some always have their boyfriend come over and spend more time with him than the kids; some get fired for putting the kids in danger. Nannies are not licensed, unlike daycares. It's very much parent-beware, and a lot of people don't have time to search for a good nanny, hire them, and monitor them to make sure their kids will be safe.
There's also just a convenience benefit from having your kid on-site. You can share commutes; you can use the carpool lane; your schedules are identical; you can pick up your kid in a blink if they get sick; you know they're always close; you don't need to coordinate logistics with a nanny; your time schedules will overlay; and so on.