Sorry I don't have any first hand knowledge of this matter but I recall reading what I felt was a fairly plausible account of Tiger vs Sherman combat that said something along the lines of.."The Allies" meaning tank crews? If what has been speculated in this thread is true (not sourced, but I assume the respective people could do so if called upon), those crews were probably drilled on maneuvers in platoons of five tanks that could reliably take on Tiger tanks. It's not my area but one person who did explain it to me once, admittedly fourth-hand or so, was that it took that multiple tanks to outmaneuver the Germans and get someone into a position where they could take a shot at one of its more vulnerable sides.
If there's truth in that, or at least if it's not too wildly off what the original explanation was, then it's not so much that you will lose about five Shermans to kill a Tiger as that you need larger numbers of Sherman tanks operating in tandem in order to expose the weaknesses of the Tiger tanks.
I don't know if this is the truth or not, but it at least sounds plausible, and perhaps someone can confirm it.
"Usually cost a Sherman" ie a group of several Sherman tanks could expect to take down a Tiger tank but they could expect to loose a Sherman tank in the process. I didn't get the impression that it was considered usual to loose most of Sherman tanks involved.