A question about the market

I was always a bit confused by the market. Lets say I have some decent build order and I follow it and have no need/very rare need to use the market. I end up in the mid game castle age and see the market is still at full prices/sometimes even above starting prices for food or wood. Is it worth to grab that extra gold for selling first few hundread resources? If yes, at what time in the game? If i see high prices is it good idea to preserve my gold and send more vills to wood/food? At what point stop selling? At 60 gold/100 food/wood? 50? 30? 14? What do you guys usually go for? Im talking mostly normal civs and not saracens. I always tend to ignore the market until late imp when i doscover that my opponent already sold stuff and prices are bottomed out.