First of all... Screw building your own cables... buy from http://monoprice.com
you'll get better quality than "monster" and it will be even cheaper than building your own... Not to mention it has nothing to do with the OP's question.
As for the REAL question being asked.
The short answer is... you can't convert the signal don't even bother it's not worth the effort.
The parts list to build your own HDMI to Component converter will run you MORE than $200 easily... that is if you want decent quality. It will also require a great deal of technical knowledge as it will require the use of FPGAs and some custom circuit printing. the $160 converter is cheap for the kind of signal processing that's going on.
If you want to upscale movies over component video... buy an Xbox 1, hack it and install XBMC... you can upscale your movies all day long with that.
Look for DVD player hacking sites... some DVD players can be hacked/modified to allow region free playback and or HD output over component video... the problem is the MPAA wont allows DVD player manufacturers to output upscaled DVD playback over component for fear that it will allow people to easily rip off the DVD. Early Oppo upscaling DVD players and many no-name Chinese upscaling DVD player will allow HD over component.
Buying a well know name brand DVD player will only really get you one thing... and that's a DVD player that conforms to the retarded DRM whims of the MPAA and locks you out of enjoying your own paid for content.... aren't you glad you spent the extra money to have valuable features removed under the assumption that you're a criminal?