How many free copies of a textbook is a publisher typically willing to provide?
You have to understand that in the undergraduate textbook market, the publishers are competing intensely for textbook adoptions and will do what it takes to make the sale. (This is not so much the case for e.g. the monographs that might be used in graduate courses). The marginal cost of production of an additional book is very low, people who get desk copies were quite unlikely to purchase for their own use, and so it costs the publisher very little to give out desk copies ad libitum.
At my large R1 school we have different TAs for our intro classes every quarter; sometimes ten or more of them. We have no problem getting desk copies for each TA.
Former Pearson rep here. This is how it works:
Pearson (and likely others) clamped down hard on reps over-sampling desk copies a couple years ago so any faculty paying attention will have noticed a dramatic shift from 2010-now. Specifically, when I was a rep I had a "budget" for physical books that was merely theoretical, and set at about 4,000 copies for my territory. The year after I left it got cut in half to 2000. If reps go over, they pay out of commissions for the overage. So Pearson finally (wisely) incentivized reps not to send these out willy nilly.
If you're getting lots of service from a publisher rep, it's not always because the class in question is large. It might be because you're married to the woman who makes the big decision for the intro Chem course across campus, or because you do teach that large intro bio course every 18 months. The opposite holds-- getting poor service != your class must be small. If you have a bookstore that never orders in high quantities, you're not actually a customer of that rep as much as you think you are. The used market will take the whole cake. So in the case spelled out in a comment above (no copies till the store orders), the rep is likely trying to put the hurt on the bookstore by getting faculty set against them. It's a risky strategy imo because the rep's relationship with the bookstore is so crucial. But I'd have done it at one school where the relationship with the bookstore was beyond salvageable the day I first came in. But all in all, your best bet for getting a desk copy is really quite simple. for those having Trouble:
Half the time when I didn't send a desk copy it was on accident. I have a post grad degree and have done a little in the world of academia. Was on my grad program's "big" fellowship and also taught some courses etc. I was insanely busy. I was busier as a Pearson rep. Just ask again and again. The software is crap and it's a nightmare for reps to handle this logistically, but the sales teams don't want it automated as they want to intercept the BIG requests as a local rep so they have knowledge of where the large adoptions in their territory are happening. I dropped the ball all the time for small clients (who truly do not matter from a sales goal perspective, but toward whom I didn't have any intention of being a poor rep--they just come in below the line). An email a week later would really seal the deal, or a text message or phone call for sure. There is a 100% chance a rep doesn't get all the things done every day they need to get done. In my territory anything under 50 books never really got done but I had three huge-course schools (and two small schools I never Even visited). My calculation tells me to spend 88% of my time at 2 campuses, 12% at a third, and 0% at four and five. Which also means I have a Bad relationship with the bookstores at 4 and 5. If you teach at four and five, you have to have a class with like 400 kids in it for me to really wake up biting my nails over forgetting to follow up with you (agh the pain I recall from biting my nails all the time during these years at Pearson! But not from schools four and five)
If they want you to take a digital copy and you want physical, same policy applies. Just keep asking.
If you get blacklisted for suspicion of selling copies on to the used industry it will be tough to get copies. There is a way to see this in the reps system but it's going to still be at their discretion to send or not (you have a flag on you called "bookgrabber" at Pearson if you're suspected of this). But this is pretty rare.
If you can't get what you need, you could have your chair request by phone. That would work for me with a small course.
Last resort, email the editor. Don't talk shit on the rep; the editor will surely know what's up--they won't tell you but they will know immediately whether it's a case of "agh that terrible new rep in Oklahoma is killing my adoptions!" Or "yeah that's totally reasonable that the rep skipped this one" but all editors are basically nice people, young, but smart, more academic in their pursuasion, and they care more about small courses because the individuals they need to Court are the influentials in any field, which means that while no rep gives a shit about Vassar or Swarthmore or your R-1 upper division physics course, the editor is genuinely incentivized to care. They also maintain solid relationships with reps and will manage the politics of you going behind the reps back pretty well. Edit to add: to find editors, check the copyright page of your old edition. Or used linked in. Or find the authors email online and ask who they worked with. Authors are quite accessible and friendly (most make zilch and really do believe their book can help you and your students -- many, even top names, include their email in an intro and literally invite students and faculty to send questions to them.) current editor is always incentivized to get X $ in business in the fiscal year and also to cultivate long term relationships with future contributors, authors, reviewers. Tell them you like to review in their field and you'll get your desk copies -- even if they just mail them personally off their desks.
Maybe this is helpful.
I personally consider textbook publishers to be somewhere between an unethical business and organized crime.
They rip off your students, so don't feel bad about getting as many copies as you can squeeze out of them, and then some more to give to your students.
Most books are printed overseas anyway, at a cost of ~$5 each. You can imagine how much they make on a single book. Elsevier has roughly 7 billion EUR revenue and a profit margin close to 40%
If there is any alternative, I try to go for books that are cheaply available to the students, and for books that don't randomly change the enumeration of homework assignments to make older editions useless.
I think it is time for us to push back in the interest of our students. Our department decided not to go with books that needs to be 'registered' online to be usable. That was a good first step.
I wish university libraries would provide textbooks. They have a much larger buying power, and would end the textbook scam very quickly.