The government has published indicative guide prices and information on calculating costs for developers buying statutory credits.
They start at £42,000 per credit for a low distinctiveness habitat, up to £650,000 for high distinctiveness habitats (lakes).
Defra notes that buying statutory biodiversity credits is a last resort option for developers unable to use on-site or off-site units to deliver biodiversity net gain (BNG). Developers must buy 2 credits for every 1 biodiversity unit they need to compensate for.