As a current member of staff of Gamestation I would just like to add some things to help give clarification.
1. Mass Effect has dropped so much due to not selling well upon first release unfortunately it came out in the year where it had titles like Halo 3 to compete with and iirc it came out the same week as Pro Evo 2008 which is always a mistake cos the only games that will rival that in sales are Halo, GTA, and Fifa.
2. The offer should be on for at least 2 weeks, I cant give procise date due to the fact at store level we will only find out 1 (maybe) 2 days before customers do.
3. Games like Kane and Lynch not being reduced will be due to Eidos not allowing some redemption on any sold (unlike Bioware).
4. "Deals of the Week" are negotiated possibly a week in advance so generous companys (such as Activision for COD4) will allow us to buy as many copies that we feel will be neccesary, however some companies cannot supply us fast enough. For example Lego Star Wars Complete Saga, great offer but they couldnt get us enough copies for the Wii which was a bit crap tbh.
5. Lastly, there is no conspiracies going on, we dont offer something then hide all the stock we have of it. Alot of people over the xmas period called me a liar and claimed I had loads of stock of Wii consoles in my stock room and was just trying to create a hype, not true. In stores we have targets to meet which means if we got it we will sell you it
Hope this helps you out