the depression was caused by merchanting stopping and creating inflation, but there is no inflation in runescape. therefore, prices would stablize. There is inflation in runescape it just does not affect everything, such as items sold in the shop that are easily bought aka -Noob stuff found in general shops- and the price would rise. Look at it this way if there weren't merchants there to bring you constant flow of supplies, you would either need to get them yourself or find a needle in a haystack to sell to you and they could charge what ever they wanted because it would basically be a monopoly, if no one else was selling those items. Merchants are like stock brokers, they bring the items your looking for to you with out you having to work as hard.