Hi agupte,
I can only speak to the quality of the materials and help you identify any weak links in the mattress but only you can decide on which ones provide you with good PPP. which of course would also be a significant part of your personal value equation.
1. Berkeley Ergonomics:
They use all high quality materials and they also use better quality European innersprings than the norm (rather than the more standard Leggett & Platt that are much more common). No weak links and relatively good value as well.
2. Keetsa Tea Leaf Classic:
I would need to know the specifics of the layers to make any meaningful assessment. If they contain more than an inch of 3 lb memory foam I would avoid them. They are a Chinese brand made by Zinus and while I don’t know if they changed their materials as far as I know none of the Zinus brands ever used 5 lb memory foam.
3. RoomandBoard:
I believe that the polyfoam they use is low density (1.2 lbs) and I would want to make sure. If this is the case then I would avoid this mattress.
Their latex / innerspring hybrid uses good quality latex (natural Dunlop) but their coils are probably not in the same quality/performance range as the BE (theydon’t provide the details) so overall these would be “better than average” value but not in the best value range but they also don’t have any weak links based on their website specs.
4. Mattress Factory, Fanwood, NJ:
Again I would need to know the specific layers and components to make any meaningful comments. They make some very good quality mattresses with fair value and they are also very knowledgeable but may also be in a little more premium price range than some other local manufacturers (but the specifics are important to make comparisons).
5. ABC Home – OrganicPedic Slumber:
This mattress isn’t listed on the OMI site or on the internet so I would also need to know more details to make a meaningful comment. OMI as a whole makes some very high quality mattresses and they use inner tufting for their cotton layers which keeps them from shifting which is a more costly “hand built” construction method but they also tend to be higher priced than other mattresses that use similar materials and components (sometimes significantly). Again they don’t have any weak links.
If you can fill in some of the gaps I’d be happy to add to my comments.
Have you considered or talked to Dan at Bay Bed and Mattress who are a member here and make component innerspring/latex mattresses that can be shipped anywhere in the country and offer layer exchanges as well?
I don’t think that’s too likely because I enjoy what I’m doing too much … and there are many great manufacturers that already do a great job (that have decades of experience with manufacturing). About as close as I get to manufacturing mattresses is talking to some manufacturers about various designs and ideas that they are thinking about producing and acting as a sounding board or providing feedback … and that’s close enough for me 
Phoenix