I went because a good friend told me that she got her pregnancy tests there, for a dollar of course. The awesome thing is that either her doctor or a nurse told her about it! Turns out, that is where at least that doctor's office gets their tests. I don't have any cited source or research, just word of mouth. However, I don't doubt it since I found that Dollar Tree does have a websitefrom which you can order in bulk!
I've been using these, and they seem to work fine. This is great news if you're hoping to have a baby and want to be able to check more often without throwing away $15-$20 every time!