In Amazon's defence their billing system is far more complex than Google's, not because Google have done some marvellous job on theirs, but because it is a solid decade younger and hasn't caught up with all the bells and whistles yet.
The price you pay for an instance not only depends on what you've already spent up to that moment in your account, and all accounts attached to the same organization, but also any reservations in those accounts which may /float/ into your account should they not be used in their home account, and crucially, _the price varies according to what you use, and every associated account uses, in the future_.
Finally at month end, your entire account receives a bulk tiering discount that cannot be calculated until your full usage is known.
If you have 1x t2.medium reservation and there is already a t2.medium machine running in the account, the price displayed would likely be the on-demand price. However, if after starting your new t2.medium you kill the old one, the price _applied_ will likely be the reserved price -- so long as both instances did not use more than 60 minutes runtime in that hour.
You can however, get a reasonable preview of your daily spend with 24 hours lag using Cost Explorer, which I think is more than resonable considering it is a meaningful, comprehensive account view, and not some tiny datum associated with a single item on your bill. For anyone spending serious money with either Amazon or Google, there should be a large upfront modelling step involved before stuff starts to get purchased, no per-item price preview can avoid that.
Meanwhile I wonder if Google's display price reflects sustained use discounts or committed use discounts. Given how underbaked most of Google Cloud is, I suspect (before ever having to look!) the answer to that is a resounding "no".
So the question becomes, would you prefer no information, or information that may be off by in excess of 70%?