check out this article,
http://en.wikipedia.org/wiki/Time_value_of_money
and learn to do this in Excel. (follow the "calculations" section in the article.) It's pretty clear that 50k 10 years ago is still less than 75k today, but if you ever have a question about it, check in Excel. (use the functions: PV, FV, RATE, NPER, and PMT)
On the other hand, you may want to stop comparing to others all together for the most part, because it does you no good. You can be an excellent work and do a great job and still not be paid well or as much as a corporate lawyer or surgeon. So much depends on your field, your company, your negotiations, etc. etc.