let me assure you that that is exactly what you do
PBL I think that what you say is a bit misleading. Let me first put this another way to see if we actually do have a disagreement.
In taking legal action it would be foolish not to take into account the ability of the other to frustrate your goals by legal stratagems, legal delay and the application of superiour resources to escalate matters. A wise litigant will understand their level of financial exposure (and add a good %age as well). I too think that this is true and it seems to be consistent with what you have said.
But there is something missing in all of this. Other things matter too. One would be the significance or strategic import of the matter at issue. Another is the actual merit of your case. This, to put it mildly, matters. Here I speak of the "facts" - the issue in dispute, the quality of the evidence, the real intentions of the opposing action, the relevant law, etc.
When you make the decision to fight such considerations matter a lot. In fact, they may justify the taking of relatively high risks in terms of costs. The issue under discussion here seem to me to fall into this latter category.
Without such a balance your statement can easily be reduced to the following somewhat ridicuous conclusion: "If I am sued by somebody with superior resourses I should give in."
BA are playing a game here. BALPA is playing their part in the game. It may be a serious game, but the moves have a logic which has a lot more to do with issues other than cost. Context is all. I think BALPA have correctly interpreted BA's intentions and the risks. Strategically I think they have little choice, but I also think their's is a better case. But none of us knows what a court might decide.