I'll defer to Al as best-selling author. What I could get an award for is worst contract negotiator. I always suspected my contracts weren't that great, but I didn't know how not great until I joined TAA (Textbooks Authors Association). Contracts are often discussed on their listserv, and everything they tell you not to do, I did. Some people there apparently are receiving 15% on COVER price, which I thought was unheard of. I have a sliding scale starting at 10% of net price, and it's not even the "good" net price that the listserv lawyers advise, it's the crappy net price. Here's what my Cengage contract says:
"Net Receipts shall mean gross receipts by Publisher from all sales less any itemized taxes, interest, finance charges, insurance, packing, shipping and transportation cots and less any credits or refunds for returns and any credits, rebates, bad debts, value added taxes, discounts and promotional allowances to customers."
I did see that before I signed, but thought it was normal.
As for PH, they're famous (infamous) for selling books to their own overseas subsidiaries, counting them as "low price sales" and then paying no or very low royalties. They were sued for this by the authors of a popular text (they were cheated out of hundreds of thousands of dollars in royalties with this accounting practice) and settled out of court. So the lawyers on the list advise striking the clause in their contract that discusses sales to overseas publishers and just say that all sales shall be at the same royalty. Of course I have the original clause.
Oh well. If the books go into second editions, I'll renegotiate, even though -LOL- there's also a clause saying that all subsequent editions will be done on the same terms as the first one. I also don't GAS about other things in their contracts, such as rights of first refusal, not being allowed to write a competing text for another house (lol, kma) etc. I've broken those contract clauses already and don't care.