Hi Kay, it's tough for me to estimate prices since there's no standard that everyone adheres to, prices seem to vary across the country, and most importantly--I really don't know the condition of the machine! If there is something seriously wrong with it, $30 is too much; if it's in perfect working order, I'd pay $30 for it, but that has to be modified by the fact that I live in NYC, where $30 for anything is a steal; and I also don't have to pay a repairperson to go over the machines that I acquire, as that's my hobby.
The bottom line is, a vintage sewing machine is worth whatever you're willing to pay for it. I've found that no matter what price you pay, you'll eventually find out that another person paid half of that for the same machine, and yet another person paid double.
- Rain
Vintage Singer Sewing Machine Blog
http://vssmb.blogspot.com/