Im always in 2 minds about Resonance's releases. In terms of the quality and detail that goes into the packages themselves, they are top-notch. The booklets are always comprehensive, with plenty of interviews with key players, and photos of additional material which were tracked down for the release. The sessions and usually worth of release from a musical perspective too.
Their downfall is the recording quality. I believe they do the best with what they get but are clearly limited by the tapes. RSD is another topic in itself but I imagine that Resonance almost has to rely on the ability to charge significantly more during this period because their overheads will be so high. From what I understand they make sure that the estates of the musicians (or musicians themselves if they are around) get a decent cut. They often cite their close relationships with the likes of Bill Evans and Wes Montgomery's estates and I imagine those relationships are partly built on them making sure everyone gets paid their dues. Plus the packages themselves are often luxurious with trifold sleeves, thick glossy booklets, etc.
It's a tricky situation for sure. Are they all worth their £80 asking price, not in my opinion. But when you then look at other RSD packages which clearly are cash grabs (with the artists likely getting little to no input) it puts it into perspective a bit more.