The average "price to book" ratio for bank takeovers in Australia since the recession almost two decades ago was 2.1 times in the seven transactions completed in the two decades since Australia's last recession. CBA is paying BankWest 0.81 times net assets, with an effective purchase price of $2.46 billion.Westpac is paying 2.7 times net assets for St George in an all-share deal.The purchase price of CBA's cash takeover of BankWest is 12.1 times 2007 earnings, which compares with an average of 17.2 times in comparable transactions.These comparisons exclude the Colonial rescue of Trust Bank in Tasmania in 1999, a transaction completed at higher multiples than the present one.BankWest will return "excess capital" to HBOS of $360 million while CBA will also repay $530 million in preference shares. Taking this into account the discount to net assets is more like 15 per cent than the 19 per cent promoted by CBA. CBA is likely to sell the new shares to fund the acquisition at the low end of the suggested range, or $38, and a 15 per cent discount to its last share price.