From my experience so far, ilvl 30 gear makes mostly lvl 1 materia and a little lvl 2. Lvl 1 craft/gather materia goes for 1k on my server and lvl 2 10k max depending on which type it is so.... no you couldn't make anywhere near that in 4-5 hours. Also it relies on a being in a group which a lot of people don't have if they're playing the odd hour here and there, it takes considerably longer to SB gear alone. So unfortunately this doesn't work for a lot of people.