I've been thinking about this, in general, and I don't know the specific answer to this, because I know it depends, but, this is my feel for it, on Fast game speed.  (150 turns/game).

If a Farmers/Makers/Market/Science Quarter takes 3 turns or less, that is cheap!

If a Farmers/Makers/Market/Science Quarter takes 5 turns or more, that is expensive!

My feeling for a faily priced Farmers/Makers/Market/Science Quarter is 4 turns.

Likewise, in general, I feel the same way about Research. 5+ turns = expensive. 3- turns = cheap.

Also, true for Feasts/Faith/Parade too.

And, then considering infastructure too.

Except, this is not the case with Military units.  They are always a value, so long as its relevant either Tactically, or with regards to Pop Growth.

How does everyone else feel about it? What is cheap vs expensive to make/create in a city?

Usually, the decision, as I see it is, When do I balance the Building Stars from Industry, compared to Science Stars on Research?  Do I focus on one of them first, or do I try to balance the decision all along?  How much of a lead in one category is excessive, compared to the other?  Whereas, the money resource, I see, as delayed industry, in general, which is important to store when things are expensive, and technology or influence can expand resources in the mean time.  Of course, I'll purchase anything that is 20 money or less in a city though, just to get it completed, and have the use of for 1 more turn, especially if it expands resources.

Speaking of production, the cost of quarters in dynamic, so I usually try to make as much of production as the newest infrastructure cost divided by 2-3, so I can finish them in 2-3 turns. If so, then I stop building makers quarters and start to produce science/money (depends on specialisation of city) and farmers quarters if there lack of food.  So, usually if you finish latest infrastructure in 1-3 turns that means you can build any unit in 1-2 turns (on normal speed). But usually if quarter will be build in more than 5 turns in already developed city, than that means there is lack of production. On fast speed it is 3 turn usually 

EsoulBoy wrote:

Speaking of production, the cost of quarters in dynamic, so I usually try to make as much of production as the newest infrastructure cost divided by 2-3, so I can finish them in 2-3 turns. If so, then I stop building makers quarters and start to produce science/money (depends on specialisation of city) and farmers quarters if there lack of food.  So, usually if you finish latest infrastructure in 1-3 turns that means you can build any unit in 1-2 turns (on normal speed). But usually if quarter will be build in more than 5 turns in already developed city, than that means there is lack of production. On fast speed it is 3 turn usually 

Those numbers are a nice rule of thumb that I find I use myself.  I'll build districts if they're fast (and if I can spare the stability), otherwise it's infrastructure or more Makers for me, yup!