Nope. Test fee is not correlated with the difficulty. MUET is tougher than IELTS for me. I took both papers. 3 times taking MUET and always a band 4 for me. Took IELTS once, and I scored band 8.0 without attending any classes.

For me the Speaking test in MUET is very unpredictable. They don't actually test your fluency but rather your arguments and some questions presented is quite weird (for me I guess). There was one time I had to argue on which household item is the best and I got an iron. Their speaking test also relies on your team mates, if they face difficulty to present their opinions, you can't create a dynamic interaction between everybody.

I was trying to aim for Band 5.