I looked at Bradco literature over a year ago. The price was around $5,000. There's a couple of options such as width, depth and type of teeth. There was a limitation of 30 pto hp.
You'll also need an HST or a really really low creeper gear. I found a used DuAL, bought out by Woods, which is similar. The DuAL and the Bradco will go down around four feet. If you have a lot of rocks, the trencher won't work well at all. It will drag up some impressive rocks if you only have a few embedded here and there depending on how far down they are.
Trenching if you're going deep is also not fast. It's probably faster than a backhoe for narrow utility trenches since you don't have to continually move and setup.