What they meant was that the LGPL is perfectly fine to use for commercial use, but you have to a) provide the source for just the library when requested (easy enough: provide a link), and b) allow for the program to run using a different or modified version of the LGPL library that's used.
That means you can dynamically link QT, and your program doesn't have to be (L)GPL. No commercial license required.
It is, but LGPL does not mean what you said it did. It doesn't force you to open your code if you allow users to replace the LGPL components. If you don't want to do that or run in an environment where you can't do it, then you have the option to buy a commercial license to free you from these restrictions.
