Enttec's Open DMX USB, SKU 70303, is a USB-B to 5-pin DMX output in a folded metal case, priced at $70. It gives you one universe of 512 channels and nothing else.
Enttec are unusually honest about the omissions, and they matter. There is no standalone playback, no MIDI, no configuration software, no firmware updates and no LED indicators. The device has no buffering intelligence of its own, so timing quality depends entirely on the host computer and driver. For a fixed installation that has to run unattended, spend more. For a bench rig where a laptop is already in the loop running the show, it is hard to beat.
Paired with free control software it turns a laptop into a strobe and colour controller for a cymatics rig, which is the use we care about here.