[Avodah] offering a higher salary

[Ben Waxman]

I've seen posts claiming that it is forbidden to offer cleaners a higher 
salary to work for you. While I can understand that it makes sense to 
say that no one can break a specific agreement for a specific day of 
work, why should it be forbidden to offer a higher salary to someone who 
has a long term agreement?  A, this is the common practice in the high 
tech world and I have never heard anyone say "Assur". It would seem that 
there is general agreement that this halacha simply doesn't apply today.

Second, how can anyone be meshuabad in such a way to one person? Does a 
person wanting a higher salary have to simply quit without any idea 
about having another job?

Ben