I would worry that this transaction is being set up primarily as a tax dodge. The Government has been aggressively targeting tax dodges over the past several years.
The purpose of the transaction appears to be primarily to either a) avoid estate taxes, or b) establish a high cost basis that eventually benefits the buyer when they sell.

I would not stick my neck out on a transaction like this. You can probably get away with transactions within 15-20% of comps, since it might be harder to prove that it was overpaid. But a 100% difference would likely stick out if there is any screening going on by any law enforcement agencies. OR even worse, it will likely get noticed on one of these housing blogs as such an outlier that would raise suspicion.