Ah-h-h, the Prepress Department . . .

This is probably the most nebulous, and therefore the most dangerous area in the art of putting ink/toner on paper, on signage, bottles, windows, t-shirts, whatever. Output devices & their specs (esp. color profiles) change, industry-standards sometimes aren't, and a few production shops still use Adobe V6 (& industry-related) apps from 2013 - while designers (& their files) usually have "the latest, greatest" Cloud updates . . .

Time spent on conversions & "we had to fix it" charges at these output facilities (vs. the estimate) can escalate quickly . . .

So, Flying Dutchman has to be very flexible in order to cover all output scenarios > the same basic design intent, but alternative appearances on signage/billboards, or cut vinyl, maybe embroidery, plus the more typical print destinations - brochures/flyers/POP, the web, etc ...

Commercial printers, specialty item providers, the daily/hourly e-mail "drops", social media "marketers", weekly/monthly bound print publications > most print shops and/or marketing wonks, have no file submission wiggle room. If said vendor is desirable enough, they're very, very busy, and therefore, very scheduled ...
Plus (of course), always right ...

Aggravation has to be nipped in the bud . . .

$90-$135/hr. is the common range for charges, if said shop makes "those changes" in-house, THEN deadlines become threatened (naturally). As a prepress/graphic design concern, WE are the responsible ones - not only for translating the designer's files (and/or, ours) to said production environment, but also for preparing the client for those "unforeseen" revisions (and, the associated fees & delivery delays) . . .
Oh, and yes - we've been known to "eat" said charges (even when we're just the messenger) . . .

What SHOULD save a designer's tush is the ability to see potential problems early - before the job even gets to the prepress proofing stage - e.g. explaining why the client's RGB computer monitor "view" ("see - right here ... THAT'S the green I want!"), or a PMS ink color vs. its' process color (CMYK) "match", rarely looks the same > esp. "your screen" vs. the final, "printed" piece . . .
Plus, no commercial prepress shop wants to get involved in any explanations as to what's entailed in the arcane world of color space/color profile translations, ink saturation/dot-gain coverage, plus proofing vs. final print variations - but Flying Dutchman IS built to be able to handle the occasional teaching atmospheric & the inevitable heartache . . .

Sometimes, the diplomatic effort necessary in trying to "improve", or "smooth out" the client's inconsistent grammar and/or writing style, can easily become counter-productive . . .
"Helpful hints" can be less than welcome . . .

So, creating a continuing relationship with a client (you) should involve an easygoing trust factor - but, proofing perceptions & output snags exist ("press checks aren't free?"), "expert" (but non-tech) opinions from print salespeople (who may need an intervention), or pressmen having a bad day (press checks again), and the "we've gotta catch a plane to Vegas on Friday" deadlines, may all rear their ugly head . . .
Amazingly, even a sense of “what are you trying to pull?” might emerge (from either side) . . .

Sincere smiles, & the hand-holding function will always be with us, esp. when keeping costly surprises at bay - but, not being rusty (esp. technologically) really helps limit the scarring . . .

We ARE sincere (yep, the Truth can hurt) . . .