Art can be taken as a hobby or as a career option too. Everyone is artist in their own interests. I am also an artist because I like drawing and writing. Nowadays, artists are selling their arts too expensive. Why art can be so expensive ?
First of all - the art market is highly speculative. Art is very scarce resource. Generally, when an artist makes a work of art - its one of kind- like a painting. Thus individual works of art are more valuable than mass produced products like those thing you buy from "Walmart" that say "Made in China". This also made in China, but this is not of a kind.
So, in general, things that are unique often have a higher value in our society. You can always build another million dollar home, but you can't paint another Monet. Because Monet is dead and this is a reason why sometimes and artists way will become more valuable when he or she dies. Because they are not really around to produce more, which makes the work that they created while they are alive kind of a limited resource that can,t be further produced.
Some artist also become famous and fame can often drive up your salary. because the relationship between prize and value is seldomely a linear one. Its almost always a power law distribution.
Also, some artworks have historical significance. For instance, painting of kings, pops and historical events like French Revolution. Many of these artworks may have been the driving force behind historical change and that is definitely valuable.
It is fact that artworks are priceless because they have been deemed by the society to be important artifacts of human civilization. There were people who literally risked their lives and died protecting these artworks and protecting the artifacts of our collective cultural heritage and that's priceless.