You can't use MAKE illegally, because it's FREE..
And you can't use MAKE instead of PRO version, because MAKE have no PRO features.
If during the months, you can do your work with MAKE version, then you don't need a PRO.
So, the main idea is to have a PRO features, only when you need them.
I doing my sketch for a months, and then I need to export it to CAD format just once.
Well, it's very weird to pay full price for a function which will be used for a 1 second.
I doing my sketch and I need to use Solid Modeling Tools(PRO feature) all the time, and I need for example do production of construction drawings from time to time.
Then, obviously, I will better buy full license, because I need PRO features very often or even daily.