What are the costs of releasing a Blu-ray (compared to DVD)?

[VarHyid]

I hope someone here has some insight in the industry to shed some light on the costs of releasing something on Blu-ray vs DVD. To be clear, I'm talking about a situation where the content is already fully mastered in HD incl. all special effects etc.

The reason I'm asking is because multiple times I've been in a situation where something I was looking for wasn't available on Blu-ray even though I know for a fact that it exists in HD.

One such example would be the second season of "Stargate Universe". Recently during the whole Black Friday and other holiday sales, I finally decided to buy all the Stargate shows. SG-1 is only on DVD and it's unlikely that'll change - fine. Stargate Atlantis in on Blu-ray - good. Stargate Universe, well... kind of. There were two seasons and only the first one is on Blu-ray. IMO this is ridiculous. I understand that the show didn't make a lot of money, but how much would it cost them to release it on Blu-ray since it already aired in HD?

Another example would be an older show called "Numb3rs". I loved it, wanted to buy it recently and it turns out it's only available on DVD... yet it's available in HD on the US iTunes Store so an HD copy exists. Any costs associated with preparing it in HD are already spent so now it only comes down to just authoring the content for the disc and physically printing it on the disc. Is this really so expensive that the studios would only "risk" it if it sells millions of copies?