I saw that thread too. And it explained that if a tructure was built and not bought then upgrading a similar type structure over it in the future would cost less to quick-buy. This is because the quick buy is taking into account the production that already went into building on that tile. I think that thread was more specific on the math involved.

However, in this case I'm talking about a previously unused tile. And in both cases I'm talking about the quick buying. It cost 204 if you chose the clinic and then buy. It cost 438 if you choose to build it first and then buy. If it matters I'm playing as the Yor.

This is similar to what you might experience playing as the Thalan and buying factories. Whre it cost you less if you first pick build and then buy. So in that case you are buying something thats already in the build queue. Thats kinda weird and a killer if you dont know about it. But at least we know it happens due to their super ability.

As for the fertility clinic, i can't see any reason for the behavior i described.

I use it on planets that i conquor from my enemies. After invasions the population is quite small an at that stage of the game paying 204 (or 438 ??) bc for a qucik build of one is no big deal. The AI planets usually have at least one emoty tile or morale structures you can build it on.

On planets tht flip the population is usually maxed at 6b and so ill quick build a farm and then queue up a fertility clinic.

I may try a theory if you'd care about reading through...

This has more to do about the pending value of a (to be or)completed building than where it's being built.

The Fertility Clinic is a special case as it is providing Pop-Growth boosting; if you were to hit the buy button BEFORE you had anything properly selected right on the surfaces, costs would remain constantly the same.
But, as you have it focused straight into the project box... it is directly taken into account by the engine so the 'projected effect' can relate to the 'exact amount of hammer requirements' whilst being memorized for direct construction made of cycle_by_turns expenses as usual OR (and this is exactly why cost differs) from a preset figure in Hammers that must be applied to a rush bought asset.

Very complex principle to grasp without a metaphor, i guess;

The architect plans must de drawn before a construction crew goes to the location -- but, the warehouse can still be filled up with all the material necessary for some inventory maintaining COSTS. The longer this stockroom stays idle, the higher heating, electrical bills will get. Until, a truck backups, fills and delivers the products to workers for assembly. The overall spending applied to a finished HQ downtown - is the sum of its parts no matter when (how much for, too) they're accumulated and affected to financial liabilities slot in a statement!

Sort of a Fertility clinic which has yet to distribute phamplets to population wanting to have more kids with specific medical help. But the resources must be kept available by onsite staff.

Serious, that's exactly how i perceive this issue! Game-wise it may just be a lot simpler but call me, an administrative freak.