Where did you buy it from and how much did you pay for the digitizer, if the supplier you bought it from buys it for say £10 and then marks it up by say 30% then they will sell it for +- £15, if you buy one for £45 and the mark up is the same then he has paid £30 and chances are they will be of very different quality.
Even eBay suppliers have a set markup and dont just suck a price out of fresh air and i can assure you that there is a reason why they are cheap and probably 2nd grade or very bad copies from a factory in Chengdu China.
I have fitted a lot of digitizers and have tried many suppliers and have a box of them that are faulty and if i put them side by side i can see the difference in quality compared to the supplier i use to buy all my apple spares from now.
My answer is a bit long but im just trying to get across the point.
You pay cheap price you get cheap quality.