Robert on what evidence do you base this belief? PLEASE show me a wider field of research than your father/cousin/brother/great auntie Jeanie!! I suggest you get your nose out of the gutter press, the most likely place for you to find this kind of opinion. Look at it from another point of view...
If people took a cut in their wages, do you think that would stop an employer (look at Nike again) who decided to move to a country where labour is much cheaper? Until the 80s/90s manufacturing and skilled manual jobs were in the west. Today, as someone suggested earlier, we focus on eg finance,banking call centres. These jobs are ALREADY moving to countries like India. I know that I couldn't live on the average Indian wage, could you? Companies spend more on advertising than they do on labour costs. I made that point earlier, maybe not clear enough. If a company wants to move, they will give any old excuse. The oldest and the best of course, is the one about wages being too high.
More generally, on the question of whether or not unions are needed...
The nature of trade union organisations:
Trade unions are as strong or as weak as their membership.
Trade unions do not EMPLOY workers, by and large, they represent them in conflict with employers.
Trade unions represent workers, eg in discussions about pensions. If a worker is getting a crap pension deal, that worker has the right to argue for change. He or she has the right to argue at various levels, workplace, shop stewards' commitees, branch level, national level etc... The worker may or may not choose to take up that argument. If he or she takes up the argument and fails to win it, then he/she follows the decision of the majority. If he/she does nothing about it, then how do they expect change.
This is a fairly sane and rational process. You recognise it maybe? Yes, of course, it's called democracy. Why do you have a problem with whether we need them or not?