SDI Interfaces - Are they all Expensive

[samsc]

http://www.aja.com/d10a.htm

does this work with rgbhv, how do you connect it up with a vga source?

http://www.vtx.co.uk/video/digiboxa2d.htm

this is only component?

do any of these cheap ones convert dvi or vga directly to sdi?

I know the expensive scan converters do this.