"Very cheap insurance, but if your airline thinks the bulbs are more important than the
safety of the airplane and all aboard, that merely proves my point."
Agreed, but it might not be quite as cheap as you think
Sure, bulbs are relatively cheap, but if you start adding labour costs, cherry picker hire/purchase costs (if we're talking 747's), delay costs (if headed to a place where logo lights are compulsory),...
Some aircraft now have 3 lamps per side (probably not for visibility, but for redundancy).
Rgds.
Q.