I do have a complete collection, including many duplicates, of black rainbow early releases. They are not particularly rare, except in pristine condition, but on a desirability scale (to a "completist" collector) many of them have monetary value.
I don't think that SH.tv would help much to determine value in that way. The place is peppered with completists, though.
You might enjoy to peruse their marketplace, but last I noticed, it was mostly SH remastered CD releases which changed hands, as it should be I suppose.