I do not really believe that this is the main reason.
To be very clear, if Germany decided today that 500,000 young, male, healthy new workers are needed, they could simply "open their borders" and make it publicly known that they need these people and start the selection process.
Of course, such a move would be highly controversial in any country (Germany is not any different here), and likely would not sit well with many voters, giving them a reason to vote for right-wing parties in the next election. So yes, it is possible that the current government uses the humanitarian crisis to get people critical of accepting foreigners to be more accepting of the fact.
However, those refugees are housed in refugee camps, fed, clothed, medically treated at the expense of the German government, and they are not required (or even allowed) to work. Possibly in a few years.
What I personally do not like about this line of reasoning is that it gives other countries a very convenient excuse to say "Ah yes, they do it for the money, not because they want to help. Well, we have enough people, so that is why we can not take any refugees".
I was just putting it there for people to see the stats for migrants needed by Germany. I think Merkel has been very clever in the way she has handled this crisis. I'm just pointing out that Germany has self interest in taking these people for economic reasons. I didn't realise it was such a controversial thing to say.
