Something else to think about is that it's generally better to have one big turn than two middle sized turns. That's why cards like Giant or Ranger are better than their averages.
In the case of a payload card like Giant I agree as you can use it to get Provinces.
In the case of a terminal draw card like Ranger I disagree; in a deck-drawing engine you want 1 or 2 pairs of Rangers and it wouldn't matter if Ranger alternated between drawing 2 and 3 cards instead of 0 and 5 instead. The former can be even better as it makes your engine more consistent.
Half-Market is probably somewhere between those two cases.
Front loading all of the draw to the first Ranger is great for consistency.
Sure but Ranger is not a card you want to use as mini Tactician, you want to play them in pairs and have an even number of them in your deck. Also, Ranger takes time to kick off as the first one is dead. If tempo/sifting matters a lot, e.g. in a Travellers game, a plain Smithy might be better (admittedly it probably isn't because of Ranger's extra Buy).
I'd price blinking castle at $3 to begin with, I think it'd be quite strong there so maybe it'd be better at $4.
$4 is too much. It is not like Market is a powerhouse $5. Just imagine that there are other Peddler variants in the Kingdom. You wouldn't really want to pay $4 for a half-Peddler with a half-Buy on top of it (unless you need the Buy but that applies generally for +Buy card; Herbalist isn't good just because you sometimes need to get it).