Though I think Regent is great, I don't know when they became a "mid priced cruise line". I get emails from them every second or third day, and about the cheapest I've seen averages $300 - 500 per day per person.
That's only "mid priced" if you are booking suites
I'd be looking in the $100 - $150 PP per day range if I was looking for mid-sized.
My recommendation would be to make sure you travel when schools are in session, and probably on Princess, Celebrity or NCL.