Note that a manufacturer writing "low cost" does not automatically make the true.

The next problem is that a manufacturer claim may be true when you build 10k units, but the cost of building 10 units may be extremely high, because the need for custom-winded coils or components that are very high to buy in smaller volumes.

To know the real cost of a device, you really have to do what Erik did - open the links to the individual application examples and take a closer look.

If he did look at an application example for a 500W design, then it follows that the 1kW or 2.2kW designs will not be cheaper.