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 many production shops have Adobe (& industry related) apps from 2013 - while designers (& their files) usually have "the latest, greatest" updates . . .

Time spent on conversions & "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 job, but going to signage/billboards, or cut vinyl, maybe embroiderers, and the usual flyers/brochures, the web, etc. Commercial printers, specialty item providers, weekly/monthly publications - most have no file submission wiggle room. If said vendor is desirable enough, they're very busy & therefore very scheduled - and, of course, always right . . .

Aggravation has to be nipped in the bud . . .

$75-$90/hr. is the common range for charges, if said shop has to make "the changes" themselves, plus deadlines then become threatened (of course). As a prepress/graphic design concern, we are the responsible ones. Not only for translating the designer's files (or, ours) to the production environment, but also preparing the client for any unforeseen revisions (plus, associated delivery delays) . . .
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 it even gets to the prepress proofing stage - e.g. explaining why a PMS color vs. its' process color "match" won't look the same when printed (as opposed to the client's computer monitor "view" ("right here - that's the green I want!") . . .
No commercial prepress shop wants to get involved in detailed explanations as to what's entailed in the world of color spaces/color profiles, ink saturation/dot-gain, plus any proofing vs. final print variations - but Flying Dutchman is built to be able to handle that occasional teaching atmosphere . . .

Sometimes, the diplomatic effort necessary when trying to "improve" the client's inconsistent grammar and/or writing style, can easily become counter-productive . . .
We know that those conversations can be less than smooth . . .

So, having a continuing relationship with a client (you) should be a help/trust factor - but, proofing perception issues ("press checks aren't free?"), non-tech "expert" input from print sales people (who may need an intervention), or pressmen having a bad day (press checks again), plus the "we're on a plane to Vegas tomorrow" deadlines, may all rear their ugly head . . .
Sometimes, even a sense of “what are you trying to pull?” might emerge (from either side) . . .

Sincere smiles, and the "hand-holding" function will always be with us, as we keep costly surprises at bay - but, not being rusty (esp. technologically) really helps limit the scarring . . .

We ARE sincere (but yes, the Truth can hurt) . . .