In anything wireless.. just like anything else.. "You get what you pay for"
I have a Crown Wireless Headset and an Audix Headset now BOTH going to an AT UHF wireless Transmitter/Reciever I'm not going to mention the expense. because most couldn't afford someone to engineer it.. I had one of my guys do it on my bench for 1/3 the price, and it's cleaner than most.
I would even use it live it's that clean.