You don't offload things to the client in order to save money. You offload things when it will improve performance. Most of the processing power and bandwidth will still be incurred by the server, just at a different time in the lifecycle of the app.
If your page takes 3 seconds to show anything at all, your bounce rate will be stupid high.
If your page loads nearly instantaneously with placeholders, and then the content loads in over the span of 4 seconds. Your bounce rate will be significantly better.
Even though your page loads slower, it will be perceived as faster resulting in less users navigating away before your page starts rendering.
Perceived performance is only one factor but there are many other reasons why you offload things to the client.
You don't offload things to the client in order to save money. You offload things when it will improve performance. Most of the processing power and bandwidth will still be incurred by the server, just at a different time in the lifecycle of the app.