Upload & Sell: On
+1 @ much of what has been said.
One thing to realize is that light emitting (light generating) monitors vs. light reflecting (light absorbing) prints are going to be different relative to the ambient lighting in the same viewing area.
The monitor is adding more light in addition to the light in the room. The print is subtracting (absorbing) some of the light. As such, it is difficult to expect the two to look the same. This is essentially what people are trying to get you to understand when they say your monitor is too bright and that you need to turn it down / calibrate / use icc profile as a means of giving you a preview that tries to compensate for this difference.
One more way to think about it is to consider artwork that has a dedicated light above it. If you took away the light above the artwork, it would become darker and more muddy looking from the ambient light only. How much light we put on the print from ambient only or ambient + will impact how much light is returned/reflected to our eyes. So it is with the monitor view = ambient + monitor.
As an extreme example:
Consider that you are sitting in a dark room viewing your monitor. You get everything just the way you want it and hit print. You walk over to your printer, pick up your print and look at it. It looks virtually black (the lights are off). You walk back over toward your monitor and as you get closer to the monitor, the print starts to look a little brighter as you approach the light being emitted from your monitor. Eventually, you put your print right next to your monitor and it looks as bright as it possibly can, but it still doesn't look as bright as your monitor.
Now, you turn on the lights in the room. Your monitor will appear to have a lower contrast than before and the print will appear brighter than by viewing in the darker environment ... but they still will not match. They will certainly be closer than when we first picked up the print off the printer in the dark room, but they still aren't going to be the same.
The dark room example is obvious, because it is well, so obvious due to the stark difference. With the lights on in the room it is "less obvious", but the difference remains.
Ambient + monitor emitting = light reaching your eyes will always be more than ambient-print absorbed = reflected light reaching your eyes. If A=ambient, M=monitor emitting light and P= print absorbing light, then: A+M>A-P. Because your print is absorbing light, it can never really look quite the same as your monitor, particularly if we are viewing a jacked up monitor, viewing in a dim/dark room or both.
So, to get them to better match, you'll need to calibrate your monitor / lower monitor brightness / raise ambient in monitor room while editing. Or view/display the print with more light falling on the print to "compensate" for the absorption of light vs. emission of light. Some folks contend with this by soft proofing, others have developed a strategy of adding some % of brightness/curve to their files after they get things were they want them, etc. More than one way to approach it, but first you have to recognize that a difference @ monitor vs. print exists.
Note: +1 @ the profile difference is another piece of the puzzle as they (different profiles) place the numbers (R,G,B @ 0-255) in different areas on the color map. The printer may not be mapping the same as your viewing profile does if you are viewing in a different color space/profile than the printer.