About me: it's more origami, you know the Japanese art of folding paper, usually without using glue, scotch tape. So only sheets of paper that hold each other thanks to locking mechanisms.
Regarding origami you can find many kind of origami: animals foldings, tessellations...I am more into geometrical origami, and more precisely modular geometrical origami. The word "modular" means that you fold many times the same module that you assemble after to each other. A bit boring to fold the same module dozens and dozens of times (especially if this module requires a lot of steps to finish!).
Yes it's difficult!
First you need to understand the folding steps (and the diagrams that are not always clear enough...). Then you need to be super precise, because if you repeat the imprecision many times then the final object may be a bit less solid. But in any way, we are not machines, and thus the imprecision is not avoidable, the goal is to try to minimize it as much as possible.
Another difficulty comes from the choice of paper: a too thin paper is not suitable because the locking mechanism may not work properly, but a too thick paper will be impossible to fold if you need to make a lot of folds....
The last difficulty is to assemble the modules: you need to assemble them in a specific way, and to try (by using paper clips of other "devices" for example) to maintain the already assembled modules while assembling others...Not so easy...Plus the last piece is usually very hard to assemble because of the forces created by the already assembled pieces.
I put below some of my origami. Hope you will appreciated the shapes and the colors used.
I may sell some, drop me an email is you're interested!
The price will depend, of course, on the difficulty of the origami, on the time spent on it, on the choice of paper ("premium papers" are expensive!). But in any case the price will definitely be undercharged simply regarding the time spent (multiplying a chosen rate per hour by the hours spent on a model would definitely result in a very expensive price!...an origami does not take 1 minute to fold sorry to disappoint you ;-) ).
Some geometrical structures
Who can name them? ;-)
The one on the right is a bit loose (but still cannot fall apart) because more modules are used to make a hole.
With only one sheet of paper
With subway tickets (nothing is used to make the tickets hold!!)
Around 300-350 are used for each.
Other geometrical shapes and miscellaneous