Ironically, it’s easier if you don’t pay Qt and just use it as LGPL: ship it unmodified, distribuite Qt sources unmodified on request, and go your merry way.
This is theoretical for me. I am small company and have no time/desire/money for lawyers to decipher all those intricacies of LGPL (also they say that some stuff there is GPL). I prefer to pay reasonable one time fee for permanent license and upgrade when I feel it is needed.
Maybe to you. To me it reads like: do not ever touch this tool to do anything that has even remote chance to go commercial.