Stonemasons versus Battlefield Construction

Two civs get a card, 'Battlefield Construction', which you will occasionally see included in their decks, as it permits their musketeers to construct specific buildings (barracks, stables, and outposts for Ottoman, barracks, caravanserai, and castles for India).

If you assume that the time your military spends building these structures to be of no cost, then the question becomes, how many of these structures would you need to build before the value generated would compare favorably to, say, a 600 wood crate?

That crate is worth 1,125 seconds of villager time. (1200 seconds for the wood minus 75 seconds to unpack the crate).

Barracks/Stables/Caravanserai/Foundry: 30 second build time Castle: 60 second build time

So, in order for Battlefield Construction to pay off, you'd need to build 37.5 barracks/stables/caravanserai/foundries, or 18.75 castles. My point being, in a regular supremacy game, crates, even mediocre ones, handily outperform the Battlefield Construction card. But let's suppose you're playing a looong game, and you think over that time you might build that much. This is where the comparison to Stonemasons is invited. Rather than saving 100% of the build time for these specific structures, you'd save 65% of the build time for all structures, including walls and town centers. Anyone with a passing familiarity with FFA or Treaty matches knows that tons of wall building goes on, along with plenty of mills, plantations, town centers, etc. Plus, these buildings will go up faster, which can be critical, such as when you're trying to repair defenses after they've been breached.