Benefits:Access to a larger marketIncrease in production of goods
Costs:Loss of jobs in developed countriesDepletion of natural resources.
On the one hand, a global market means that a company or firm can potentially reach a larger market to sell its products and services. And in turn, make more profit. On the other hand, it also means that the competition is global and that a firm has to compete in this larger market with hundreds of firms. This often means that to be competitive, companies have to lower their costs. One easy way of doing that is by outsourcing or moving parts of their production process to countries with lower salaries. This leads to the loss of jobs in the home countries.
The increased competition and the larger market also mean that more goods are produced at a better price for the customer. However, this production can easily get out of hand and deplete natural resources.
An access to a larger market means that there are more ways tha tproducers can sell their products and more exports. Since exports are in general beneficial to a country's economy, we have that the first is a benefit.
The loss of jobs in developed countries is because there is cheaper labor elsewhere. The people that lose their jobs have a very hard time and this is a bad thing.
Globalization leads to more needs for production in order to accomodate the massive sale of production. We have that several natural resources like oil and wood are depleted and this posits major problems to humanity's survival. This is a cost.
The increase in production of goods is a benefit. Thanks to globalization, there are many technological goods available to most people and not just the rich ones. Also food production has gone up and there is less hunger.