I swore by soft proofing on my monitor until a client's 4 foot banner came back looking like pea soup
For 3 years I trusted the soft proof view in Photoshop and never asked for a hard proof, because the colors on my screen always matched what I sent out. Then in March I did a 4 foot banner for a diner in Akron with a deep red logo, and the shop called to say my file was set to RGB and their press would have to guess at the values. I switched to converting everything to CMYK myself and ordering a $12 proof strip before the full run, which added two days but killed the surprise. The red came back dead on the second try, and I have not sent an RGB file to a printer since. What do you all charge clients when a proof adds a day to the timeline?
Learned that lesson the hard way too, sent a bright orange logo to a printer as RGB and it came back looking like burnt pumpkin. Now I convert everything myself and pay for the proof strip every time, that 12 bucks is way cheaper than reprinting a banner. Honestly I just eat the proof cost and build the extra day into the quote upfront so nobody's surprised.