They ARE selling well, but they are NOT selling ( nor being produced) in the quantities that some deluded people think. The misconceptions come from the observations people have of their local stores; they either find them mostly sold out, or not in stock at all--and they hear a claim or two from someone else elswhere and conclude that they MUST be selling out nationwide.
It overlooks the fact that these are being made in much smaller amounts so the supply is more accurately meeting the actual demand.
10,000 DC figures ( and example) selling out to 10,000 collectors is a "success" ( because it sells out), but that's just 10,000--something like Star Wars sells well over 100,000 of a given figure. The DC figures cannot attain , or sustain, those kinds of stratospheric sales numbers to make them a true sales success and THIS is where the deluded are tripping up.
The projections and expected sales figures for these toys are VERY tame compared to the truly popular toy lines these days (Star Wars)--the fact that they sell out in many places simply says that the supply is adequate to meet the demand. (Just look at the pegs space for DCUC and Star Wars for the biggest hint...)
And if anyone doubts that... look no further than Hasbro's Marvel Legends wave 1, in which they themselves got suckered into the same delusions--and produced quantities that far outstripped the demand. If DCUC was produced in quantities that the deluded THINK the market supports, we'd see these toys peg-warming in massive amounts.
The current marketplace cannot and will not sustain that kind of thing, especially for a toy line without other media support at this time.
The quantities that Mattel are making and the demand are clearing allowing this line pay for itself, but they are not lighting the world in fire with the profits.
This is why the line maintains a strict policy of extensive re-use of parts, top-tier characters in each wave, re-issued characters with no C&C parts, and no vehicles or playsets planned--simply because cutting productions costs means they stay profitable.
Let the truth be told. DCUC's production numbers are tiny. Nuff' Said.