This depends on many factors: brand, model, condition, location and so on.
But to be clear, while a restored stove is worth thousands, an unrestored stove, no matter what the condition, is only worth hundreds. There are VERY few exceptions to that rule – a Chambers Imperial or a Magic Chef 6300, for example.
To put hard data on it, in 2021, roughly 1000 unrestored Chambers model Cs were on the market in the US (Craigslist, Facebook, Ebay, etc). The average sales price of an unrestored model C across the US was $250. The higher prices were paid for colored porcelain. If your stove has chips in it or any damage to the chrome, the value goes down quickly. I’ve been watching the same unrestored Chambers C be put on Ebay twice a year for the past 4 years at $1800. It hasn’t sold and it won’t sell at that price. I’ve seen a beautiful 1924 4-burner sit online at $3500 for almost a year now because it’s only worth one tenth of the asking price. There’s a good reason for this.
The difference between an unrestored stove and a restored one is 50 to 80 hours worth of work taking apart every last piece of the stove, cleaning it, rebuilding it, adjusting, calibrating and testing it. Add on to that the cost of materials and replacement parts and the difference in value is clear.
A collector I know uses the rule of thumb “never more than $500 for an unrestored, medium-sized stove.” His words of wisdom should serve as a guide for buyers and sellers everywhere.