An unopened BCD536HP is worth a good deal more than $200. I have zero doubts that it could fetch around $350 on ebay.
As far as outdated, LSM aside, it's better than the SDS200 other than not having the cool display and LAN, and the digital audio being a bit muddier than the SDS200. It doesn't have the "interference" issues from nearby frequencies that the SDS200 displays in some situations (like mine). The 536 is absolutely worthless for LSM on my outdoor antenna, in my location. You get nothing but the occasional garbled audio. My current 536 is used mainly to monitor a hybrid Smartzone system, sitting on a desk.
The SDS's, at least for me, are about LSM, first, and foremost.