Ones that are no longer 100% factory original (refinished, a few replaced parts) can often be found for under $1000. Original condition pieces with 95% or more remaining original finish are a LOT more money. A 1943-vintage Colt might be worth between $2000-$3000. A contract gun (like Remington Rand) would still be about $1500-$2000.
And then of course there are super-rare variations like the ones made by Singer Sewing Machine Co.. One of those will set you back about $80,000 give or take.
I heard about that 80K singer, Is there a pic somewhere?
I know where there is a switch and signal which has been reblued and over polished for about 1K
Another remington rand about the same price and condition.