All depends on which one you want and where you look. I always aimed for the OEM equivalent brands like MANN, Mahle, Meyle, Purflux (great zigzag media), Beck Arnley and of course OEM VW. They are built much better and you can truly see a difference side by side with the cheap stuff. Interestingly enough they aren't necessarily more expensive, just harder to find.
RMEuropean.com is a great place with good prices, but I think you have to pay shipping there. You will have to familiarize yourself with the VW sites that have everything available. Like Cascadegerman.com, IDparts.com, RMEuropean.com, FCPeuro.com, Authausaz.com and there are others. When I need something, I just look across all of them and see who offers the best deal. Their stuff should be correct and of good quality.
Another thing that you REALLY need to look into is getting your timing belt replaced. They are due by time and miles WHICH EVER COMES FIRST. If yours hasn't been replaced, it is way overdue. Most of the time there is no way to tell, so it needs to be done. If that belt breaks, it is over. Also fuel filter needs to be done at the correct intervals, those fuel pumps are very expensive and you don't want to stress them out or let dirt in. Also the oil you are looking for is a VW 507.00 spec oil in 5w30. Most places don't have this.
Edit: for additional info.