The reference point that I know off the top of my head (or at least the figure that was widely bandied about on the net) was that production cost for Farscape, averaged across a 22 episode season (since some eps cost more than others to produce due to things like varying amounts SFX etc.), was approximately $1.5 million per 1 hour (less commercials) episode.
Using that as a benchmark, 20 hours of broadcast time (less commercials) would cost about $30 million to produce.
I'm not sure what the overall effect on costs would be due to differences such as having vs. not having animatronic characters, many of Farscape's alien races appearing to need more time consuming makeup, the fact that Farscape was produced in Australia, .....
Of course, the budget for Legend of the Rangers would probably be a more direct "comparable" (at least assuming the mini-series would be produced in Canada), but I don't remember their budget off-hand.