Qt can be used commercially for free. It's LGPL whether you pay or not.
Users only need to pay for a license if they want to distribute statically linked software with Qt, if it is licensed in a way that is LGPL incompatible.
Users only need to pay for a license if they want to distribute statically linked software with Qt, if it is licensed in a way that is LGPL incompatible.
This is true now, but was not always the case.
Qt is also interesting in that there is also an agreement in place with the KDE Foundation that ensures that the Qt Company will always offer the core parts of Qt under a "proper" open source license. If they choose to switch to one of these non-commercial licenses again, then KDE is entitled to release the source under a BSD license if they want