For selling items at the merchants, try to consolidate identical items..
instead of selling your Ragus leathers each time you return to the merchant, retreive the ones you already have on sale, then sell them back as a single stack.
Buyers can still buy them from the stack individually or en masse.
This can cause an early sales time out for your new items though, I am not sure if it averages the time remaining on the old stack with the 7 days for the new items, or just hits the whole stack with lowest time limit
There are ways around this, which I wont go into right now.
The other question, is do you really want all those items up for sale ?
Silan shops are filled with the crafting efforts of learner players, almost all with no hope of actually being bought by anyone else. Unless you are competitive on functionality (eg HP boosts), quality, price or scarcity (eg "high" level HA or jewels on Silan) your crafts will just get in the way of selling more stuff.
My practice is to sell craftable mats, at about 50% so people will buy them, and maybe one or two of the best results of my crafting grinding. The rest get sold straight to the NPC.