Just to point this out -- marks cannot be converted into gold. You can, however, use marks to get things (gear and whatnot) that you otherwise might have to spend gold to get. So instead of paying 1 G for a nice new sword on the AH, you can get a comparable sword from the skirm vendors with marks instead.
*quick edit* Although many things can be purchased with marks/medallions and are not bound so in theory you could buy with marks/medallions and sell them on the AH...
R5 100 GRD Marevayave - Leader of Riddermarked For Death
R8 100 MNS Fayah/100 LM Siennah/100 HNT Dinenol/102 RK Dhurik
100 CHN Alachas/85 CPT Dinfaerien/60 BUR Dhax/35 WDN Godoric
R9 105 MNS Fayeh (alt Wilya) - Lonely Mountain Band @ Landroval