There is currently a sub-$2600 RT biz fare on United and BA from SFO-LHR but it requires travel in both directions to be on off days, like M-T-W (sometiimes S or Th). Maybe you go a little earlier or later, even with the extra hotel nights, it's a deal. $10k for biz SFO-LHR rt is crazy, no one should ever have to pay that.