So I've noticed we have a card category that we've never really discussed as its own thing - Coin payload cards. These are Actions whose main function is to give you lots of money. Now, there are a lot of terminal Silver (and Gold, and Copper) cards, but most of them have that as an added bonus to whatever else they do. Woodcutter is a +Buy card; the +$2 is there to make it (almost) worth $3. Mountebank is for giving out junk, etc. But some cards either only give coin or are intended as a payload of money. Some of these do other things, but they are for the most part penalties to balance their cost.
Secret Chamber - indefinite amount - requires you to discard to get the money
Baron - $4 - requires discarding an Estate
Coppersmith - indefinite amount - requires Coppers to put it on
Tribute - $0, $2, $4 - depends on the other person's deck, and does other things, too
Salvager - ≤$11 - must trash a card first
Pirate Ship - indefinite amount - requires trashing opponent's money first
Merchant Ship - $2 this turn, $2 next turn - split between turns
Counting House - indefinite amount - requires Coppers in your discard pile
Vault - see Secret Chamber
Horse Traders - $3 - requires a two-card discard, but gives +Buy
Harvest - ≤$4 - requires deck variety, discards top of deck, requires deck
Duchess - $2 - cheap, gives benefit to opponent
Mandarin - $3 - must top-deck, can be either bonus or penalty
Poor House - ≤$4 - goes down with Treasures in hand
Beggar - $3 - requires gaining Coppers
Death Cart - $5 - requires trashing itself or an Action, and comes with Ruins
Count - $3 - see Mandarin, does other things
So why HT and not WC? WC is equivalent to Silver with a +Buy, requiring an Action. HT is a *Gold* for cheaper - the +Buy is just a bonus here. Why Duchess and not Embargo? You have to trash Embargo, and the +$2 is clearly a bonus to Embargoing a pile. I dunno, you guys may disagree with this list, but some of these (PH, Harvest) I don't think are debatable.
So why differentiate these from normal terminal "Silvers"? You don't get terminal Silvers for their money, you get them for their effect. But *these* cards you get for their money, as they give a healthy amount compare to their cost; enough that you get them *because* of the $ they give.