I have had mammograms hurt more or less depending on where I am in my cycle. Generally it's just like a bad pinch and doesn't last afterwards -- and I have very dense breasts.

However, the last one I had actually hurt much less because the clinic had upgraded their machines to a model that pinched less.

It's really hard to say, but I'd first think it's a less-skilled tech or secondly an older machine. You might want to ask your doctor, though.