Why China things are cheaper than other countries? Why Quality is differ in India & US for same thing of China

It is a Communist country. Slave labor!

Unions they drive up wages then people raise prices

China has a lot of cheap labours, hence the cost of production is cheaper. And I think China produces goods that cater to all consumers, meaning to say there are both low quality and high quality stuffs.

There are several parts to this answer which would require a book. However a few of the major items creating a comparative advantage are; undervalued currency, surplus labor, lower quality controls, lower environmental regulations, SOE's and SOE partnerships with favorable tax benefits, subsidized industry and lower governance on safety standards both on products and employment work environment. In addition, expectations of living standards are far less than the western world thus lower wages are acceptable which reduces pressure on industry labor cost; however this is changing. The abundant population reduces labor cost while allowing industry to realizes economy of scales early in production thus reduces the cost of living. This explanation is simplistic at best, but it should help understand the picture a little clearer.

Generally the Labour is cheaper in China, the Productivity is quite high compared to many other countries. Infrastructure advantage, Government policies and so on.

Regarding China quality, Though the country produces all items these days also gives quality for the price affordability for example:

If India is ready to pay $100 for a Split Air conditioner because they want to be competitive in sales with in India compromises in many parts in the A/C and goes for a cheaper version and low quality knowingly (it is a pity as a country they do not follow any specific quality conditions like ISO, ISI when imported) where as USA is ready to pay higher price and the country can afford to pay as the currency is relatively stronger when it comes to purchasing power.

More so the Quality assurance, guarantees, penalties are very high and the competition level is not on price matter it is purely Brand, quality. Government protects quality.

A similar toy (toy gun) sold in Indian Market for 50 cents is sold in America fro $5 -10 simply justifies the quality.

The expense in China is generally cheap, therefore, the salary is cheaper too.

Determining the price of goods is a basic principle of economics. Many factors are involved, such as variable production costs, and fixed production costs, the type of production system, etc. Also in the equation enters protectionist policies, tariffs, taxes, etc. In a nutshell, for many reasons (low production costs due to comparatively low wages is a big factor), producing goods in China costs less than in Western countries.

As far as quality is concerned, quality assurance (the planned and systematic activities implemented in a quality system so that quality requirements for a product or service will be fulfilled) and quality control (the observation techniques and activities used to fulfill requirements for quality) may vary from country to country, but the client (the company outsourcing the manufacturing of its products) is responsible for ensuring that the manufacturer meets its standards, and in some cases, international standarts such as CSA, ISO, etc. If the client doesn't care or fails to control the quality of its products during the manufacturing process, problems will arise when the good hits the markets...To make a long story short, China produces crappy sh%t as well as excellent quality goods.