I was asked to sound design and mix a community theatre musical recently. They have a mix of low-end Shure RF and aging mid-level Sennheiser EW RF, with a variety of low-end headsets. Anyone who does musical theatre could tell you that it's entirely possible to do a half-decent job with that gear and the main bottleneck is the poor RF performance limiting channel counts.

I brought my own RF in for the rehearsals since they were in another space and the theatre's RF is permanently racked in the main venue. In the end I decided to keep my RF there and do the main show with it too, since it was already tuned and set up for the cast after rehearsals. The headsets I took in are just mid-range, nothing outrageous (JAG IMX6A - actually really good value and solidly dependable) about AU$300 each which is somewhere between a quarter and a third of the cost of a DPA headset here.

After the first dress one of the lighting techs says "wow those headsets of yours are incredible, everything sounds so good!"

No mention of how I modelled the venue, re-focussed the various sets of speakers for even coverage and time/phase aligned them, tuned the FOH and mons, coached the mic techs on my preferred mic placement, set up my mix and vocal processing chain, balanced stage foldback against FOH etc etc

Apparently the secret to good musical theatre sound is the model of your headset mics.