Based on what I billed out at at comparable shops, anywhere from $250-400/hr. Maybe $500 if one of their more crypto-focused people looks at it, but that'd be pretty unlikely for a whole codebase.
$2000/day is what you'd pay for a web application for an appsec shop. Double that for cryptography from a focussed cryptography practice, and add 50-75% on top if you're getting reviews by PhDs at Rambus, like Intel does for new designs.