This is an ambitious ask rather than a deal: EUR 400 sits well above the EUR 230 75th-percentile asking price from 195 comparable listings, and is over twice the EUR 155 median. Even in excellent condition, that premium needs unusually complete accessories, compelling provenance, or a particularly desirable frequency band to make sense.
The U306 BPH2 is a useful, capable dual wireless system, offering two bodypacks and headsets, infrared synchronisation, balanced XLR outputs, roughly 100 metres of ideal range, and support for up to six systems together. It is well suited to presenters, performers, and small venues, but those practical strengths do not normally justify EUR 400 on the used market. At this price, verify both transmitters, headsets, receiver, power supply, antennae, battery compartments, and legal suitability of the 655–679 MHz band before considering it.
Independent perspective — not a price guarantee. Always verify condition, accessories and provenance before purchase.