The original SARH was usually reported to be a contract worth £5-7bn for 25 years. Let's call it £6bn = £0.24bn per year. I can't vouch for the accuracy of the article in the link below but Shephard's estimated £2-3bn (let's call it £2.5bn less the now infamous 20% = £2bn) for just a 10 year contract looks almost as expensive at £0.2bn per year.
Bond, Bristow and CHC shortlisted for UK Long SAR contracts - News - Shephard
Wasn't SARH originally reviewed shortly after the coalition came to power and realised that an expensive PFI was going to hoover up the nation's funds for the next 25 years? Apart from the contract length, how is son of SARH any different? £40m difference per year is loose change even for a hard up government. For the extra £40m we could have had Boulmer and Portland surviving and genuine harmonisation across all bases.
Could it be that the coalition felt the figures thrown around for the original SAR-H were unrealistically low to ensure/guarantee the provision of service required over the time period, hence the seemingly higher amounts for the Long SAR bids.