You seem to write from the perspective that the things that matter are how much money you can generate in a turn and whether you have buys to use that money. This just doesn't make sense for an article about an engine card. This is a card drawer - it restores your hand size after you've been Militia'd, it pairs your Steward with your Curses, it puts that Mountebank in your hand, it lines your Remake up with your Fortresses etc. etc. etc. Please don't write these things into the article.
There's some weird brain thing where people seem to prefer strategies which are superficially "efficient". Like they would rather get $8-9 every few turns to buy a Province than "overbuild" to a consistent deck which "wastefully" produces $12 a turn or something.
I think it's wrong to describe Hunting Grounds as competing with Gold. It makes people think "gee I've got $6 better buy Gold or Hunting Grounds." More likely Hunting Grounds is competing with Catacombs or Smithy or Border Village or it's not competing with anything.
The little commentary about your view on card pricing and Council Room is really out of place in an article about Hunting Grounds.
Hitting $6 isn't a big issue, but your article seems fixated on it. Just buy some Silvers or Silver equivalents. The price point is also a store of value, costing $6 is not always a negative and Hunting Grounds offers even more benefit for trashing. It is an expensive engine card though, so yes it loves all those things that make games longer: discard attacks, alt-VP etc. etc. etc.
So Hunting Grounds is quality for money, and that one extra card is more than it would at first seem. As such, Hunting Grounds is best when your source of +Buy is on the more expensive end - Market, Festival, etc. If there is cheap +Buy - Candlestick Maker, Market Square - you're more likely to be interested in spamming cheap engine parts than investing in a few quality cards.
I don't think the expense of the +buy is relevant to deciding about Hunting Grounds. The other kingdom cards are going to have a lot more impact on whether I am getting HG or spamming cheap engine parts. Stef's point (I think) is just that Hunting Grounds is good with restricted buys because it takes fewer gains to reach similar levels of draw, the on trash ability is extra VP gaining, and the estate can be a 3 pile thing.
There's no special synergy with "engine pieces that produce coin" and I don't really think Procession is worth singling out either.
It's really weird to say it antisynergizes with megaturn decks. Megaturn decks are just engines with really explosive payloads, there's no reason Hunting Grounds can't act as the draw that puts Bridges/HoPs/whatever into your hand.
I wouldn't say "Most often, you'll want to gain the Duchy." I think this would be empirically false for my games, but that's just my guess. Either way, whether you take Estates or Duchy is really context dependent and I wouldn't stand by any of the generalizations you make in this section.
Please don't add random bits from this post to your article, much rather see anything I criticized removed than anything added.