Yes, it's rough, but the fact is there are people who will do this sort of work for peanuts - just for the love of the work. Whoever made this trailer put a lot of time and effort into it, and I doubt he or she drew a paycheque.
The problem with that - I say as someone who started out in fanzines and kept editing one once he'd become a filthy pro, which I probably shouldn't have done - is that...
People who do it for love, not money, can back out ('let you down) if they get disillusioned, have a family tragedy or illness, or whatever. Sometimes they just give up, sometimes they come back later. But eventually, there's a month when your real life seems more important than your hobby.
But if you're talking about releasing a commercial project, into shops or just via the BBC online shop and comic shops, it has to be done by the deadline, so it's there for the agreed release date. Hence everyone gets paid, and if you let down the other people involved, you lose your money and maybe have to pay for the inconvenience caused to the company and the other collaborators.
And that's before we get into the question of copyright (for starters, those photos which are being used to produce likenesses of the characters? The actors, or their relatives, have to be contacted for their OK for the usage, unless their contract Oked their usage back in the 1960s. Which, obviously, they didn't - hence the early 1980s Star Trek comics where one-off characters from the original series who reappeared almost never looked like the actor who played them...)