WD Red vs Enterprise drives

What are the differences between the red series and the enterprise drives?

I mean the red drives has to be meant and built for all day activity 24/7..

But why does the enterprise drives cost almost double that of the red drives?

Aren't the red drives as stable and reliable?

Both drives are for 24/7 operation but the Enterprise version takes it further and uses parts/warranty that are outside the consumer range.