Both need to pass in order for one to be added, for obvious reasons.
Dynamic vendors would entail a limited stock quantity in stores, with higher end things being set to lower stock values. These stock values would reset every 60 minutes and as stock falls out the prices increases by a percentage.
The player market would allow for buying/selling items and would make way for crafting and sale of higher end goods, thus allowing players to buy/sell catalysts and finished products and/or shop stock in order to supplement the boring style of static and fixed vendors.
Tl;Dr: vendors have limited stock that as it drops it increases price by .1-2% and goods can be bought/sold on the market by players