Holly Montag celebrated her 26th Birthday party at Empire Hollywood in L.A. Saturday, a get-together that ended with Stephanie Pratt arrested for DUI.

An interesting subplot? The absence of Speidi, a.k.a. Heidi Montag (Holly's younger sister) and her husband, loathesome PR mastermind Spencer Pratt.

It made little sense that the gruesome twosome wouldn't be on hand (and makes even less that they have not commented on Stephanie's arrest since).

Well, according to reports, Heidi Montag was invited, but was a no-show. The reason? No one was willing to pony up cash for her to come. No freebies!

"Holly wished her sister could just be a sister and stop by her birthday party, but Heidi only goes places if she is getting paid," an insider said. "I mean, this is her sister and she wouldn’t even show up without a fee. That’s disgusting."

Would it surprise you if Heidi wanted to be paid to associate with Holly?

The evening did get some publicity, however, as the b-day girl’s BFF and The Hills star Stephanie Pratt was arrested on suspicion of a DUI after leaving.

The 23-year-old She-Pratt has a prior criminal record, having been arrested in Hawaii on both second-degree theft and drug violations back in 2006.

"She usually doesn’t drive to parties and is always really careful," an insider said. "Her mother is devastated, she is with her at home trying to lay low."

Ironically, Holly's drinking problem was the focal point of Tuesday's The Hills.

Neither Spencer or Heidi has commented on Stephanie's incident. Moreover, Speidi issued a denial of the above story, but only through their rep.

The rep said Heidi wanting to get paid to come is "absolutely not true." That's it. No hilarious statement from Spencer himself. Something is amiss.