Mary trulia is not as up to date as the MLS. The listing agent could have simply fogot to change, could have changed it and has to wait until it updates, or it is an automatic feed from his compay to trulia and as you, some companies sites do not update their listings as they are changed in MLS. If you are interested in more infomration or in seeing this property please let me know, i will be glad to help.
Unfortunately, there is a lag between when a price change hits MLS and when it is reflected on Trulia. This lag could be upwards of a month depending on the where Trulia is pulling the information from. For example if they are pulling the listing info from Print Media (Homes & Land), the price will reflect what is in the publication. You have manually change where they are pulling the infomation OR you have change the price yourself (although it's not gauranteed to remain -- trulia may update with the higher list price.)