according to this

http://www.neogaf.com/forum/showthread.php?t=149234

its a paid replacement (20USD/15EUR/10GBP) applicable only to MGS games after the warranty period. different publishers have different replacement plans.

anyway, all disc are warrantied for 30 days in most officially supported countries. but some poor folks who got riddled with the bad batch of DOAX2 NTSC/J Asian discs are still reporting problems