Hi Bob,
Here's the thing: If you go to Steinway Hall in NYC, Steinert's in Boston, or wherever, they'll be at least four Steinway D's available for the concert and rental program. If you try them out, one will be bright in tone, another mellow; one will sound full-bodied and rich with overtones, another one thin with pure fundamental tones; one will have a firm action, another a lighter action, etc.--with other pianos falling in between. That's because artists have different needs and expectations. Another consideration is the particular repertoire on the recital program. Mozart sounds better with a more gentle sound, while Rachmaninoff requires thunder and lightning. If none of the pianos quite hits the mark, then the artist chooses the closest one and tell the technician exactly what is desired, and it's regulated accordingly and put on stage. The next user, of course, might very well not like it, and so it will be re-regulated... again, again and again. So basically you can regulate the instrument however way you want it, whether the piano is new or used.
As, for a range, if you have something quite minor, the price could be gratis. Most tuners charge nothing additional if it takes a couple of minutes to do a few quick fixes after tuning. At the other extreme, if the work will be significant, your cost might be $75/hour and up, depending on the local market. If it will turn into a very substantial project such that you want a partial rebuilding the instrument (e.g., new strings, hammers, shanks and flanges, full action regulation, replacement of key and balance rail punchings for example), you might be looking at $5000+. I hate to say it again, but "it all depends".
My sense is that if you leave regulation to the dealer, they'll likely spend the least amount of time necessary and possible to take care of basics and the obvious. The more they can minimize time and cost in preparation, the higher the profit margin they squeeze out on the sale. Once you have your own (soon to be found) tuner-technician, he'll do whatever it takes to make you a totally satisfied customer.
For example, that Baldwin SD10 you saw that you disliked represents a serious lack of dealer prep. That's not at all unusual, in fact it's classic. Many many people have remarked that they've spotted an intriguing piano, but have had no way of evaluating it, as it has not even been tuned, there were painfully obvious mechanical issues, etc. Basically, the dealer uncrated it, put a bench in front of it, and raised the lid. Why? Because until someone actually expresses interest in closing a deal, only then will the dealer spring into action to spend resources on prepping the piano. Up until then, for the customer, it's all a matter of blind faith. Otherwise, the piano continues to languish on the showroom floor like a diamond in the rough. There is no Baldwin SD10 that when put ship shape cannot very easily go head to head with a Steinway D and hold its own. There's no good excuse for dealers dealing in neglect. That's why it'll be key for you to find your own tech to evaluate the used instrument that rises to the top of your list.
My experience with actions is that the the more noticeable the let-off, the firmer the action tends to be. The more imperceptible, the lighter the action. If you've got a top notch teacher and ask his/her opinion, they'll almost invariably tell you that a firmer action is better for learning, practicing and playing. It affords better control which leads to more even playing and a better technique overall. A light action can quickly lead to sloppy playing. Before you ask a tech to take the let-off below manufacturer's specification, I'd give it serious thought, as it might not benefit you in the long run. If you're a casual player (who sits to play a few popular tunes every few weeks or so), it won't matter. If you're a serious pianist preparing and playing standard repertoire, it will matter a lot.