Ummm, this only applies to today's financial world.

Bitcoin's price continues to go up faster than almost anything else. That can be seen as a return.
There will be a time when you won't be capable of spending all the bitcoin you have. (while living normally)

There was a time when you saved up enough money to cover expenses for your elder years. You didn't have to work because you had a nest egg. This was during a time of solid money.

Again, we will have solid money, and also, have adoption meaning its value increases as more people want it.