Nice covers and a nice selection of different cachets:
Scan #1: Artcraft (Mellone #11)
Scan #2: House of Farnum (Mellone #7)
Scan #3: C. Stephen Anderson (Mellone #10)
Scan #4: W.M. Grandy (Mellone #18)
Unfortunately, as to your question of value, I'm sorry I can't provide more positive information, however as is typical of most first day covers, there is no longer much of a market for them. They were issued in such vast quantities (nearly 200,000 for this issue alone) and although they are listed in the Scott catalog as having a "value" of $12 apiece, that's typically inflated to reflect a dealer's cost and overhead to keep that specimen in stock. Typically sales on the secondary market from collector to collector are in the 10% to 20% range of that figure. You also have to take into account the condition (yellowing, stains, corner folds, etc.) which diminishes value, and addressed covers such as yours typically sell for even less.
A good indicator is to check
ebay auction listings occasionally and see what the sell for there. In just checking
ebay, covers similar to yours are being listed from $1.50 to $10 (depending on whether or not they are addressed or contain certain cachets) with NO BIDS on any of them.