They charge for interview because they do not want you to cost them any money.... they might even make money on you....
If it was to keep every TDH from wasting time in the sim, maybe they would invite people for assessment with more consideration and caution. The way things are at the moment, they can have a wider choice of people and it does not COST them a penny..... On top of that, only money can buy you a way into a job, not merit.....If you do not have the dosh, but you are good, NO JOB!
They do not really care if you make it on the TR course or the Line Training..... I know guys who struggled big time on the TR course or who even failed line training or base check..... They did not cost the company a single penny. Come on, think!
This is what you need to remember! They do not value staff! You are just a commodity.... if you are willing to accept that, fair enough..... maybe once you are in, you will change your mind.....
Have a browse through PPRUNE, and open your eyes. Having a jet job is not the ultimate goal in life, above all with such a company. Is it?