Ruger mini's are like every other gun that is selling well - demand drives prices up. Ruger is selling everything they can produce these days, so prices creep up steadily. Ruger hand gun prices have also gone up a lot in the past 5-10 years, same reason, popularity and steady consumer demand.
Every local store around me has several mini's on display and they all claim they sell very well. I know I like my mini 14 Ranch so much, I've got a mini tactical coming in tomorrow (Ranch has a 3-9x40 leupold going on it, and the tactical will have a Burris fastfire II on it - the GG&G mount setup). Davidson's had a recent posting of 8-12 of their black laminate specials, and they sold out in less than a week (the web offers in my area were in the ~$700 range for those).
So no, they are not exactly inexpensive anymore (few decent firearms are seems to me), but they are well built, absolutely reliable, and more than accurate enough for the purposes I put them to.
Check CDNN for factory mags at better-than-Ruger prices. My shooting buddies with mini 30's do not seem to have any issues with theirs.