In online forums, the MMX 300 is often compared with the DT 770 Pro in terms of sound. The DT 770 Pro is somewhat less expensive and it is recommended to use them in conjunction with an inexpensive free-standing microphone.
However, this recommendation does not take into account the fact that the MMX 300 not only has studio-quality headphones but also an integrated gooseneck microphone, which is used in a similar form for professional recordings in recording studios.
If you consider the cost of purchasing comparable headphones and a corresponding microphone individually, the price seems rather reasonable.
Savings in terms of costs generally also mean losses in the quality of voice transmission. Which solution is suitable for which user depends on their respective priorities.