value of a vintage machine is totally dependant on your budget!
if you are in the market for a vintage machine you should set yourself a budget (the most YOU are willing to pay for one) then look until you find the right one-in your price range-
they vary in price from $25 right on up to $500+ location matters- and what a person is willing to pay-how badly they want a particular machine- if you set yourself a budget and start looking at some point you will walk into a garage- or a thrift store- or see an add---and you will know---THAT'S IT!!! THAT'S MY MACHINE! and the more you are willing to pay the better condition it should be in- with attachments- clean- working- but you need to set yourself a price limit....there are so many people now (thinking) they have a gold mine and trying to charge ridiculous prices- when you can find something better for alot less.
watch ebay- craigslist- thrift stores- antique shops- sometimes you can find a fabulous deal if you are patient and willing to wait...it took me 3 years of looking---sometimes at a great machine for a good price- i would still walk away- my hubby would assure me- you can have it if you want---and i'd just say no- that's not the machine i want---then one day i walked into a barn---and sitting there---was IT! i new right away-was so excited---would have paid most anything...looked up and asked...and the lady said (very tentativly as if asking too much) would you pay $20 for it? OMG!!! are you kidding me??? i would have paid 10 times that easy!
then i chose a whole big box of the most wonderful wool yardage---stuff with $60 a yard prices on them---i had a whole box of it---when we were getting ready to leave i said---i have this box of fabric/wools too- she said- oh that just goes with the machine! i didn't feel right about that- i knew what i had- i gave her $50 for everything...which she was reluctant to take.
so long story---
if you are patient the right (deal) will come along!