You're oversimplifying on many angles.

Firstly you have charging losses - and you're assuming that you can charge at the same rate consistently over the cycle of the charge.

Secondly, doing it like that massively reduces operational flexibility. If buses are all late back (bad traffic for example) you would want to charge more aggressively than the 60kW. You can't so you're going to have buses that are low on charge the next day.

Finally, it's all a bit moot. In most areas you do not have 3MW of spare capacity on the LV network to suddenly plug into. You're going to need a new HV connection or dramatic LV grid reinforcement, so you might as well put a decent connection in at that point. The cost is basically the same, most of the cost is in permits and civils.

Your idea to place charging points at turnaround points is also not as feasible as you make out. It's incredibly hard to do that (TfL massively struggles to get planning for a simple toilet block for drivers at turnaround points) and they are not designed in a way to have buses in a certain exact position to charge often. And even if you could if buses are late they cannot skip the turnaround like now as they need to charge. This will cause massive cascading delays down the route for the rest of the day.

Grid connections are the reason rollout is so slow, at least in the UK. There is relatively plentiful funding for it but most depots are now completely maxed out in power availability - any spare capacity has already been used and the LV DNO queue is 10+ years for local reinforcement.