first of all, from the perspective of somebody who've gone through the challenges of a PhD:

if u're planning to do a PhD and asking about how much u're gonna earn afterwards, u're setting up for a disappointment. get ur priorities straight. PhD does not mean u'll earn more.

if u wanna earn more, go get working experience. it's much easier and less stress on ur head.

the reason for my PhD?

refer to this article:

http://matt.might.net/articles/phd-school-in-pictures/

i just wanna add another dent in the world knowledge. PhD is the only place in the modern world where a mere mortal can leave his mark forever. i mean, we cant build pyramids anymore, can we? lol.

university of sheffield.

my phd title is long and doesnt often make sense to those unfamiliar with it. so suffice if i mention that my PhD is in the area of architecture education and the virtual environment. the reason i chose sheffield was that they have a leading expert in architecture education, prof. bryan lawson, which i had the privilege to become his student. at the same time, sheffield is also the top 3 university in architecture in the UK, top 10 in europe. so that puts me right in one of the best university in the world in regards of my field.

well, it doesnt matter if somebody proves it is wrong or obsolete. the point is, at the moment u submit ur work, it fulfills the knowledge gap not known at that particular time. until somebody fulfills that gap, the future researchers cant build new knowledge. so it's either u or somebody else, either way, u will make ur mark in the world. ur work will be reviewed and referred to in order to the future guy to make urs obsolete.

just like designing a PC processor. pentium 4 was replaced with a new model in less than 2 years. but it gave birth to other chips, and eventually the multi-core designs. but it all depends on the predecessors. so it's either u or the other guy. i'd rather it be mine.