Self publishing in itself means the process by an author to publish the book by himself or herself. All the activities are funded by the author in which he/she may use various service providers or an agency which is qualified to carry out all the services.
The downside is that all the cost is paid by the author , prior to the publishing of the book but the good part is that all the royalty from book sales is gained by the author. However, in the traditional publishing, the story is published by the publisher and author has noting to pay at all. The publisher carries out all the activities needed to publish the book and once the book is published, the publisher is responsible to get the book in the market. The author receive a royalty from the publisher, based on the number of books sold and the percentage fixed between the two.
When we talk about self publishing, the process is no doubt quick and easy but requires an investment in the beginning. But if the story is good, the book has very high chances of doing well. If you choose a good agency that has good professionals like illustrators, editors, designers and publishing staff, then there are good chances that book will do well and the author will recover the investment quickly.
The market has changed and more than 50% of the books are already being self published because no one has the time to receive an approval from a publisher and be ready for multiple rejections. The author has nothing to worry because self publishing is an option.
The only thing that needs to be done properly is choosing a good agency which is not very expensive and understands the needs of the author. If self publishing becomes too expensive, it loses its purpose because self publishing must be seen as an alternative to traditional publishing. Its important to do a proper research before finalizing any agency.