Swords of Yin and Yang

Name: Swords of Yin and Yang
Type: Twin ninjato
Quantity: one set of two swords
Description: The two ninjato are of identical dimensions and materials. Both blades are made of martenite, a type of steel typically used for cutting tools. Both blades have been folded ten times. They are each two and a half feet long, shorter than the average katana, to make for a faster draw. The blades are sharp on only one side, along with the pointed tip, allowing for slashing and stabbing movements. One blade is black and is referred to as "Yang", while the other is white and referred to as "Yin". The two swords are almost always used in conjunction in a Hyoho Niten Ichi-ryu fashion.
Abilities: No unique abilities.
Durability: Durability of martensite steel folded 10 times. These swords can be destroyed by weapons that are stronger than martensite steel that have not been folded more than 100 times, but anything weaker will not destroy the weapons.
History: The two blades are gifts from Jaku's parents upon graduation from the ninja academy. Knowing his fondness for blades, his mother and father had unknowingly gone to the same blacksmith with the same design for their own sword, save for the color. Only after the blacksmith created both blades and the parents had both tried to present their son with the blades did they realize their mistake. Jaku wears both blades proudly as symbols of his parents' affection.
Appearance:

Spoiler:

Spoiler:

In a technical sense folding of metal is not done to make a blade stronger but rather to mix two or more metals together so that the back of the blade can be extremely durable from a harder metal while the cutting edge can have flexibility from a softer metal and thus can be sharpened to a more fine point. So what Im saying is that basing your hardness scale on times folded isnt the greatest idea. Also if you want to do folding like a real sword it is much much higher than 10, more around 150-700x.

I've actually done research on the subject of folding blades. 8-10 folds is typically the perfect number of folds, as that gives it about a million "layers". Any more than 8-10 folds does nothing beneficial to the sword. As a matter of fact, more folds actually creates more layers, and an increase of layers actually creates more weld points, which weaken the integrity of the blade, thus making it easier to break. 10 folds is the best number, as it ensures that there are no bubbles, the elements are spread throughout the blade equally, gives it a beautiful grain, and ensures that a great deal of impurities have been burned away, leaving a better quality steel.

To summarize this TL;DR post: 10 folds is enough for me, thanks.

now that that part is squared away how about the portion detailing how folding is for mixing metals and not increasing durability? What is the strength of these blades?

It's not so much that the number of folds increases durability, necessarily, but that more folds makes the swords less structurally sound by creating a great number of weld points. Martensite steel is the steel normally used for cutting tools, so most weapons would naturally be made of martensite...
I'll change the number of folds to 1000 folds being unable to break the swords. At that level, the enemy's sword and these swords would simply clash. More than 1000 folds means that these swords would actually break the opponent's sword (leaving a jagged edge, so it's still a weapon, technically speaking).
If that's acceptable, I'll edit it to this.

So unbreakable then? This is acceptable however the price will reflect it at about 15-20k per sword just for that one part as it is a S rank weapon/armor ability.