As I said, given the changes you've noted, there seems a good chance that the EMG will tilt toward ALS. ALS often begins on one side, which may be the dominant hand side or not.
The only way to find out is to have the test (I'm presuming that it's been more than a year since the last one). If you have believed that things would stay PLS, it's no small thing to confirm ALS should that be the case. But as you point out, it could carry benefits with it, and you would be in a better position to plan.
As for decisions based on dollars, recommending a new EMG really doesn't fall into that category, nor does documenting that PLS has become ALS, if that's the case. It is or it isn't. The dollars don't make it so.
If you had a hard time at the last EMG and let the team know, if you go that route, they can work out a plan to make it easier. You can also talk with a counselor about what this decision means for you.
I think what you mean is up to 4% of the population with motor neuron disease may have PLS.
The percentages that are later diagnosed as ALS vary by how well-documented the initial PLS diagnosis was. Some of the newer tests that suggest it are not available in all areas, so the diagnostic process is not even across all states or countries.
There are probably PLS patients that get lumped into ALS from the jump, and vice versa. But that is about technology and uneven access to expertise -- an accurate sorting hat, if you will -- not a profit motive.