Right so the person they recruit should be as experienced as you then. I agree with reallytired - if they are trying to recruit another you then you should both be on similar salaries. If you end up supervising or training the other person that's when you should be complaining!
Yes I agree with everyone else. If it's the same job at the same level then unless the person they recruit doesn't quite meet the criteria in terms of skills and experience then it's absolutely right they get paid about the same as you. If you previously felt your salary was good then recruiting someone else on a similar salary shouldn't change your view at all.
As was said below, you wouldn't expect to have to take a salary cut if you moved to do your job at a new employer.
You agreed to do the job for a certain wage. However much someone else agrees to do it for, isn't really any of your business! You agreed to the wage and were probably quite happy with it. Don't let this spoil that for you :-)
Whilst I understand why this may have made you feel a bit please think about the other side of the coin - if you went into a new job with another company, why should you be paid the lowest end of the scale if you were up to the same standard, if not of a higher calibre, than Mrs Jones who had been there for 15 years? Surely you would want to be paid a similar, if not the same, sum?