One of our biggest regular money makers are sewing machines. Currently listed in the Thrifter's Field Guide are sewing machines ranging in sales price from $50 to $650. They are generally priced between $15-25 at the thrift stores (the most we have paid is around $100), but differ greatly in value depending on brand and function.
You have to look them up by brand and model number to determine value. Many Husqvarna machines are values between $100-150. But a Viking #1 will get you a few hundred dollars or more, and a Designer Diamond a few thousand.
They are frequently found without pedals to test them with, so purchase wisely! We do buy machines we cannot test at the store if they have common pedal inputs (because we can find pedals at thrift stores) if they have significant profit value for parts/repair/untested.
Sewing Machine Resale Values
The following list is based on a cursory review of recent sales, to give you a basic idea of relative brand and function resale values for a used, working sewing machine (working can include machines that cannot be fully tested but do function as much as can be tested). This list is in no particular order and is not guaranteed to be accurate.