A coin token is worth slightly more then a coin, because you don't necessarily have to spend it at the end of your turn. For most of these cards you can imagine a variant that gives coins in stead of coin tokens, and you'd just have a slightly worse card. How much worse? That greatly depends on the kingdom, the game, your turn. The important thing to remember is this: most of the time you want to spend your money. You can use it to buy better cards, which in a turn or two will generate you even more money. So the most common case is that a coin token is exactly the same as a coin. If you don't spend it, it's sort of in your savings account, except you get a zero percent interest rate. Surely investing in your deck is better then that. There are off course exceptions, and that's where coin tokens get interesting:
- $3 + $5 could be better then $4 + $4. Sometimes you really want a more expensive card to kick-start your deck.
- $7 could be the same as $6. If there are no kingdom cards that cost $7, your coin goes to waste but your coin token doesn't.
- In the endgame it can be essential to buy multiple cards in one turn
Because coin tokens are slightly better then coins, they are also slightly more expensive. This is not actually a law of the universe but Donald made sure they are. However, for most of your spending power coins is just as good as coin tokens. You want to spend it anyway! So you should try to have the bulk of your money be cheap-ass plain old coins, while only a few in the form of tokens provide you with all the flexibility you want. That is something all of these cards have in common:
the first one you buy is the best. The second one is probably also ok, after that you need a good reason to go on. Off course this reason could exist, but that's card specific.
Mass BakerThis is just not a good strategy. The idea is to load up on a huge amount of coin tokens before you ever start to buy green cards, and then be totally unstoppable in the endgame. Although it is better then greening much too early, it's also far from optimal. You will lose to someone who starts the same but then mixes it up with cards that make more money. Spending $5 on something that makes $1 each turn is simply a bad ratio. Even something as simple as Gold + Laboratory (and that's really mediocre payload for a running engine) already has a much better payoff rate.
The only good reason to get more then a 2nd baker is if they're for free. Maybe University gains them for you, maybe you Remake some Fortresses. A reasonable reason to get more is if you really like the cantrips (scrying pool engine).
Mass Candlestick makersThis is very comparable to the mass baker argument. But now the cost is not in buying the card ($2 is very cheap) but in drawing it. Even in a double tactician deck this doesn't really work out. Reasons to go on after the first two could be Vineyards, Gardens, or again Scyring Pool. But if that's not what you're going for - don't let the sweetness of your first candlestick maker lure you into buying a 3rd one, even if you have just $2 to spare.
Mass PlazaPlaza is a village and sometimes you just want those. Maybe you can cheat (draw-to-X) and then Plaza is a really good card for $4 (in those decks the coin equivalent Bazaar costs $5). If not, there is a reasonable chance mixing up plaza's with other villages is actually best.
Mass ButcherThis requires overdrawing your deck and a
lot of extra actions. It's really rare that I take 3 or more butchers. It's much more common that you want to maximize the usage of the first one or two you have.
Mass Merchant GuildDon't go beyond your second Guild unless you think you can pull off the megaturn. You don't just need to be able to buy the 3rd, 4th and 5th Merchant Guild, you also need to draw them and have the spare actions to play them. Sometimes you can and then it's very powerful.
EndgameNear the end of the game the value of coin tokens all of a sudden can go up very quickly. Buying a single province may be losing while buying zero now and two next turn is winning. The tactical decisions involved can be very complicated, but in general it's something that is underestimated. Don't spend coin tokens near the end to get some extra components, unless you really know what you're doing. Feel free to buy extra coppers with merchant guild in play.