He elucidates that acquiring incoming liquidity, essential for these types of attacks, incurs significant costs. This liquidity can be obtained either by compensating others to open channels directly or by operating a lightning node that offers valuable services compelling enough for people to initiate channels voluntarily. Riard emphasizes that the financial outlay involved in securing this incoming capacity is substantial, potentially equating to or surpassing the expenses associated with borrowing Bitcoin (BTC). For further details, Riard references a source available at Peter Todd's website.