Starting salary at Google within a given level actually doesn't matter that much, because the comp process is designed to "rubber band" your salary within the salary band for that level. In other words, you'll get larger raises if you start with a lower salary, so the difference doesn't persist very long.
In fact, when you're negotiating comp, I'd argue that an additional $1 of signing bonus or starting equity grant might be worth more to you than $1 of additional salary, because a bigger signing bonus or equity grant doesn't come at the expense of future salary raises.
However, the level you start at matters a lot. If you're an experienced industry hire who should really be an L4 and somehow get slotted as an L3, you'll spend 1-2.5 years waiting for the promo to L4. During that whole time, your peers who were hired at the correct level will be progressing towards L5. This doesn't happen frequently, but it's unfortunate when it happens. In that situation, it can actually make more sense to decline the offer and re-interview to get an L4 job offer later, since that might take less time than getting promoted internally.
In fact, when you're negotiating comp, I'd argue that an additional $1 of signing bonus or starting equity grant might be worth more to you than $1 of additional salary, because a bigger signing bonus or equity grant doesn't come at the expense of future salary raises.
However, the level you start at matters a lot. If you're an experienced industry hire who should really be an L4 and somehow get slotted as an L3, you'll spend 1-2.5 years waiting for the promo to L4. During that whole time, your peers who were hired at the correct level will be progressing towards L5. This doesn't happen frequently, but it's unfortunate when it happens. In that situation, it can actually make more sense to decline the offer and re-interview to get an L4 job offer later, since that might take less time than getting promoted internally.