Q: How much is it to install bootcamp in singapore?

Bootcamp is free and bundled with OS X. Please try Applications -> Utilities -> Bootcamp Assistant. If you do not see it, please re-install OS X using local Recovery ( OS X: About OS X Recovery - Apple Support ).

you need a valid version of windows

and if you wish to pay somebody to install it then

this is a user helping user forum we are users like you

and not even sure if official apple stores offer installing windows on users computers

but you can give it a try i guess