Heidi & Spencer

Sources close to the couple tell us Spencer's rep shot a letter to Hirsch explaining, "Heidi's made it very clear that she is not interested in releasing any tapes" ... adding, "It looks like she pulled the kill switch."

The letter also explains, "Spencer's not interested in further destroying their relationship by pursuing an avenue she's so vehemently against."

Spencer's rep also told Hirsch that Pratt "thought $5 million would be enough to convince her, but now [Heidi] is saying she'll bring out the legal team if he persists."

Steven Hirsch tells TMZ he isn't going to down to Costa Rica to meet with Spencer about the sex tape -- until Spencer coughs up a preview. Specifically, Hirsch says he wants to see at least 30 seconds of whatever it is Pratt's got.

As we first reported, Pratt is asking for at least $5,000,000 for his library of footage. Hirsch says he asked Pratt to send him some kind of preview because he doesn't want to be part of any publicity stunt. So far, he hasn't seen a frame.

TMZ has obtained an email Heidi sent to Vivid Entertainment honcho Steve Hirsch in which she says, "I don't think Spencer has any footage of the two of us. I think hes (sic) making it up for publicity for a new reality show he wants me to do but I really can't tell. He can be sneaky."

But then Heidi writes to Hirsch, "I wanted to drop you a line and let you know where Im (sic) at with all of this. If you decide to come to Costa Rica I look forward to hearing your thoughts."

Spencer insists he has a catalog of XXX videos featuring him and Heidi.

It certainly has the smell of an upcoming release.

We're told Spencer -- who's currently hocking sex tapes starring himself, Heidi and a Playmate -- still "loves" his estranged wife ... and is willing to do whatever it takes to stop the divorce.

In fact, we're told Spencer has finally admitted to having a "fame addiction" ... and wants to seek help for that too.

As for Heidi -- we're told she's down to work things out ... despite all of the public drama he's put her through recently.

We're told Heidi has agreed to listen to Vivid Entertainment honcho Steve Hirsch when he arrives in Costa Rica to make an offer on the footage ... some of which is said to contain girl-on-girl action with Playboy Playmate Karissa Shannon.

We're told Heidi wants Hirsch to provide her with the sales numbers on Kim Kardashian's sex tape -- which was also released through Vivid -- because Heidi may be interested in working out a "back-end deal" if Steve can't offer enough cash up front to satisfy Montag.

Hirsch told us he's leaving for Costa Rica sometime next week.

Spencer told TMZ over the weekend he was in Costa Rica to turn over two dogs to Heidi but she wanted nothing to do with him. The video suggests otherwise.

Spencer says he's given Heidi an ultimatum -- either tear up the divorce papers and do a reality show with him, or he'll release the sex tapes.

So we ask ...

UPDATE: Heidi and Spencer were also spotted together in Costa Rica on August 18. The plot thickens ...

Sources close to the Heidi sex tape deal tell TMZ ... Vivid Entertainment is only slightly interested in the rumored video with Montag and the Shannon Playmates. They are, we're told, way more interested in the Speidi videos.

We're told Vivid honcho Steve Hirsch is very clear ... the money tape is the one featuring Heidi and Spencer Pratt -- a tape he believes could surpass Kim Kardashian's sex tape in sales.

To sum it up ... video of Spencer Pratt is somehow more appealing than video of naked Playboy Playmate twin sisters. What is this world coming to?!?!?!?

UPDATE: Kristina Shannon tells TMZ she is "100% positive" that she is not in any sort of sex tape with either her twin sister Karissa Shannon or Heidi Montag.

Kristina adds, "I'm saddened by the situation with Heidi and my sister."

Emilio shot a dating show pilot for Spencer's production company called "Fist Pumping 4 Love." He tells us he thinks the Speidi sex tape is "an amazing idea" and he envies Spencer for it.

But rest easy -- there is no sex tape with Emilio and ex-GF Snooki. Emilio says, "Wish I did that with Snooki. But I'm still learning and wasn't as smart as him."

We're told not too long ago Spencer was at the Malibu house he once shared with Heidi ... moving out some of his stuff. Sources tell us Spencer came upon a camera with XXX video of Heidi and Karissa -- and the light bulb went off.

Sources say it was then that Spencer decided he could make a fortune selling his "library" to Vivid Entertainment -- much of it featuring naked, fornicating Speidi.

We could not reach Heidi and her reps were mum.

As for Karissa Shannon -- she tells us such a tape does indeed exist, but she's not convinced Spencer really has it. Karissa says if the tape ever sees the light of day, she'll sue the pants off him.

We caught up with Steve Hirsch outside Boa last night -- where he was definitely excited to be negotiating for the Heidi sex tape.

Hirsch says if the sex tape is going to be the biggest selling sex tape ever -- and raise Heidi's profile to Kim Kardashian levels -- it'll depend on what Heidi does after the tape is released.

Turns out this sex tape madness has been a career ambition of Spencer's for some time. He tells us he has wanted to be a porn star since the reality show "Princes of Malibu" ended ... way back in 2005.

Spencer tells TMZ he feels Heidi wants to divorce him because she thinks he's bad for her image. But, as we first reported, Spencer has eyes on doing another reality show with Heidi, saying, "We're reality stars, not serious actors. She can’t think she’s Naomi Watts. She’s a tad delusional."

As we first reported, Spencer is shopping the tape to porn powerhouse Steve Hirsch at Vivid Entertainment. Sources close to the deal tell TMZ they have heard Spencer's asking price and that Vivid doesn't think the figure is "an unreasonable price."

For his part, Spencer tells TMZ that he has an "entire website's" worth of footage, saying, "I will knock Club Jenna out of the water."

Spencer went on to say he thinks releasing the tapes will be good for Heidi, saying, "When I realized how much Kim [Kardashian] was making, my logic is this is the best thing I can do for my ex-wife. Kim is on the cover of Allure right now. Heidi isn’t on the cover of Allure."