That $20M/month estimate came when origination fees were 1%. But Lending Club has raised its fees substantially, and origination fees are now 3.25% on grade B and higher loans (most of them). They've also raised their service fees. That extra revenue per origination has got to lower their breakeven origination rate considerably.
I'm not sure, but I think the origination fees were already higher than 1% by then. Apparently Prosper got rid of its "changes" page (or at least I couldn't find it now), so I can't check to see for sure.
Also, Larsen's statement was that origination needed to be 4-5 times what they were, which would actually be about $25M -- I reduced that to "at least $20M" to account for the higher fees.
Furthermore, Larsen's statement came before Prosper's use of WebBank (whereby all loans are now originated by WebBank and then assigned to Prosper). I think it is safe to assume that WebBank isn't doing this for free. My guess is that they take half of the origination fee as payment (does Prosper's prospectus say anything about this?). And doesn't LC use WebBank too?
Thus, I bet the $20M a month estimate is still pretty much right on.
On the other hand, Lending Club didn't make cash-draining mistakes like renting an entire floor of an office tower in the high-rent financial district of San Francisco, like Prosper did, so hopefully its day-to-day expenses are lower.
Supposedly Prosper got an extraordinary deal on that space, which the previous tenant bailed on. So LC may not be saving any money there.