Can anybody explain how "Rush" buying is calculated?

I have not seen this behavior.

For me, rushing is always the construction cost not yet produced, modified by buildings like the black market, with a 25 Gildar minimum.

Can you post a screenshot or even a save?

Good question.

Base rule (i think) = production x number of turns to create with overflow.

So if you have 20p and it takes for instance 5 turns then the price will be 81 > 100 to rush the building depending on if / how many overflow you have.

More important lets say you have 50h and need 2 turns and the price is 51 its a great time to rush otherwise you just wasted 49 hammers (2 turns*50=100-51=49 wasted)

The more overflow the better it is to rush a building since you save the wasted prod  as long as u can spare the money and have benefits from rushing (more buildings faster / multiplier from city at rest) 

Things to think about:

1) There is also a minimum cost (25 gold) to rush so rushing at low prod city's needs to be done at 2 or 3 turns. (for examble if your city has 10p and it needs 1 or 2 turns you would still pay 25 gold for the 10 or 20 hammers so its bad investment)

2) Black market reduces costs by 25% so you have to take this in calculating if its profitable to rush.

So if you have 20h and need 3 turns and the price is 36gold you get 36+ 9 (25% from 36) = 45, 15 wasted prod.

What I would like to know however, do the overflow hammers count for the next project?

Havent checked myself. Il have a look next time I play.

 Edit: removed faulty mistake .

Wow. These are some complex rules you're suggesting.

I'm really puzzled.  I have been using my simple rule of thumb forever, and it has been accurate enough that I have not questioned it.  Next time I play I will pay more attention.

It's quite simple - the cost of a building is a number of production points. Each turn, the cost remaining is reduced by your production as you build it. When the cost is reduced below 0 it finishes building.

The rush cost is the number of remaining production points needed to finish it, but in gold. And rounded up to 25g if the building requires less than 25 production.

Except if you have a black market, which makes the rush cost cheaper.

Given that these two are exactly the same thing, I think that everyone looking for complex rules is mistaken.

The rush cost is the easiest way of finding what the production cost of a building is. I tend to look at the tooltips for buildings to try and work out if I can optimize the amount of production to get a faster build queue, when I have options on building clay pits earlier in the queue, or casting or removing Set in Stone or that spell that gives +1 materials.

Note that Mason and Mills discount also works as it reduces the production required.

Turns out 2 was faulty, there is no need to put a turn in before rushing, price is the same, i just had a weird coincedence when testing that, that gave the same result 3 times.

I'l edit it out.

Are there any others like black market / mason / mills?

The mill has an upgrade (30% off). I believe it's called 'Labor guild' and is one-per-faction, kingdom-only.  It has a bunch of other bonuses, too.  Probably the most desirable production building in the game.

So production doesn't overflow between buildings/projects? It really should IMO, up to a limit of one turn's production.

This. It's why I only rush buildings in cities that have a long construction time (as in, low production) since rushing a Bell Tower costs the same in a city that needs 15 turns to build it as it would cost in a city that only needs 4 turns to build it.

you don't need to know the exact math to understand it. Consider the theory: Time is money.

The amount of time a building will take, is a product of the cost of the building, and the industrial output of the city making it. When buying things, your primary goal is simply to "buy time". Specifically, to buy as much time as possible, for as little money as possible. This means there are several ways to prioritise your buying:

1. Buy more often in low-production cities. places with few materials that struggle to build their own things.

2. Buy industrial structures (workshops, lumber camps) so as to reduce the city's dependance on money in future.

3. Buy financial buildings (merchants, markets) so as to increase your capacity to buy more\

4. Buy time dependant things (like a garden, when the city has zero food) so as to save you from stagnation in your empire.

5. Buy resource production enhancements (especially crystal mines, warg dens, and influence-monuments) as these produce resources which you can sell to other factions, thus getting more money (see rule 3)

I think there is a cost multiplier for Wonders, or other important buildings. The great mill cost me a crap load more when it was 20 turns left than that Granary did when it was 21 turns. I still bought it. Capitar Credit Union brand Credit Cards have no limit.

Edit: 6. Buy unrest lowing buildings, raise taxes. So long as unrest is low, additional tax levels provide no negative and produce additional gildar. (adds to Point 3 also)

Ok my wise friends... here's what I'm talking about... how do you explain it?

I think I've got it now.  Thanks for all your wise posts!  Tuidjy, do you cover rush buying in your newbie guide?