Take a look on eBay, using the "completed" and "sold" filters.
The Fatboy especially is a high demand razor, and therefore prices are all over the place. Replates go anywhere from £90 - 195 (I believe that's what one of the restorers sells for), so absolutely mint and boxed should definitely be more, but some of them go for way less. I have seen ones go in the £100s of pounds cased with shipper etc.
Pictures will definitely help people value them but at the end of the day great photos make a massive difference and it depends what you'd be willing to accept and how long you're willing to wait for a buyer.