I only have 22 recorded prices for the JM 1894 Cowboy out of 400 total including the JM Marlin 1894C Rifle in .357 Mag. Adjusting for inflation they average within $33 of each other with the non-cowboy being the highest. My overall summary below seems to support the over $1,000 range with $1,500 a bit high but not out of the question if it's what you want. A few boxes of ammo and you won't notice. Some seller's wiggle room, I imagine.
Blue Book of Gun Values (44th Edition) indicates between $525 in 95% condition and $850 in 100% condition for this gun. I have 400 recorded prices for this model gun from $325 to $3525 over a period of 18 Yrs 2 Mos ending May 26, 2023. The average price as of that date was $851. No refurbs, no refinishes, regular sights. No distinction for import location or engineering revision, if any, no special editions, no distinctions for box, papers, tools. Current or last MSRP is $730. The last 15 prices I have for this model since 1/1/2022 range from $865 to $1700 averaging $1333.