How was the TV scam in Requiem for a Dream supposed to work?

In Requiem for a Dream, Sara Goldfarb receives a phone call and later a letter purporting to be from the television station offering her an appearance on the Juice By Tappy show. It's heavily implied that this is a scam: it's too good to be true, Sara was never expecting to be contacted (she doesn't recognise the Malin & Block company name on the phone call), there's no reason the show would contact an unknown fan who never applied, Harry is immediately very suspicious upon hearing of the offer, she never ends up on the show and the real television station staff call the police when she arrives at the office.

Let me get this straight - as the scammer, I identify vulnerable people, send them a fake phone call and application form, emphasise that they don't need to send any money, get the application form back and then do nothing beyond that. How was this scam supposed to work if no money was ever involved? I can only think of identity theft.

Some other viewers have tried to answer this by noting that Sara's return envelope doesn't have any stamps on it, which leads to a bewildering variety of speculation:

• This could simply be a meaningless (but very noticeable) oversight by the prop department because someone as obsessed as Sara would never have forgotten to put a stamp on the envelope and at least one of her friends would have noticed.
• This could be an actual in-story mistake by Sara, so nothing further happened because her return envelope never arrived, so there were some further steps that were missed out.
• This could be a stampless prepaid envelope that came with the application form, so there was no mistake (either by Sara or the prop department), so everything we see in the film is the entire plan with no further steps required.

However, all of this is viewer speculation. Is there any official answer about how the scam makes any sense as portrayed in the film? Was this thwarted by the lack of stamps or did everything happen as planned?