"We've sold 23,000 so far and that is disappointing," said Collins, "particularly so when you consider recent results, which has seen John Toshack's side beaten only once in the last eight matches.
"And, remember, we are coming into this game on the back of a fantastic win in Bulgaria only a couple of weeks ago.
Wales' chances of qualification have all but disappeared and the fans have voted with their feet by not buying tickets for what should have been the most attractive tie of the qualifying campaign.
"Germany are still a hugely attractive side to come and watch and, as such, the gate to date has to be perceived as somewhat disappointing."
Collins continued, "That said, I'm still hopeful that we will break the 30,000 barrier with people deciding to come on the night.
"I suppose, to be fair, realistically our chances of qualifying for Euro 2008 have gone. As such, that will have had a beating on the attendance."