Some of these are nice. Well, maybe all of them, but some more than others. A couple are "First Flight" covers ("FFC"), philatelic covers created to commemorate the first flight of one of the early contract or foreign air mail flights. Note the first says "C.A.M. 11" == meaning "Contract Air Mail" route #11. I don't think there is anything rare about CAM 11 FFC's, but this one is a little odd with the cachet over the stamps (i.e. the round circle with details about the flight is not a cancel, but a cachet); these are usually found imprinted more to the left of the cover. Edward Worden serviced a lot of early flight covers. I would imagine it being worth about $5.
Technically, the B.L. Rowe cover is not a FAM (foreign air mail) first flight cover as it did not carry US mail. It is a nice cover. I am not an expert at valuing these kinds of covers, but might imagine this would would be worth $20 (or more?).
The Lindbergh cover would be described as an "event cover." A lot were produced for this event, so the value is modest, maybe $5-$10. Note, when I say "value" I mean a "retail value" as you might see it selling for on
ebay. Dealers will offer you much less, since what they offer is a "wholesale" price.
The San Juan-Paramaribo cover is for the first flight of FAM 6. The leg to St. Thomas carried the largest number of covers, so this one would be worth less than some. But properly identified and promoted, it might be worth $20. The key would be to note that this is a "Lindbergh Cover," i.e. the pilot was Charles Lindbergh.
Nothing here especially rare or uncommon, but to air mail collectors still of some interest.