"So, if the recipient of the C&D letter were to offer the domain to the pursuant for, say, $500, would they still be inclined to press the case or would they pay for the domain instead of forking out $1,500? "
There is NO way to predict what they may be willing to do. Sometimes people are influenced by an analysis of the strength of their claim, and by the prospect that their claim will be contested. Sometimes, quite often, it is a matter of principle (translation: "ego") for them, and they would rather pay their attorney several thousand dollars, than several hundred to you. The theory is that if they pay you, then it becomes like feeding seagulls - if you feed one, then before you know it, you've got a flock of hungry ones following you around.
Additionally, if they file a UDRP, that is the GOOD news, since all they can win is the domain name. The bad news is that the filing cost for a lawsuit is much, much lower. I am surprised that people don't file lawsuits more often than they do, frankly. If they file in a remote jurisdiction from you, then the cost of responding is prohibitive, and they can ask the judge to award up to $100K in damages, even if there are no actually provable damages.
If you believe there is no basis for jurisdiction in that court, you might opt to sit it out and then challenge enforcement in your jurisdiction. That is generally an extremely stupid and chancy thing to do, and you will very likely end up living with a judgment over your head, which will make it virtually impossible for you to qualify for things like a future mortgage, car loan, etc.
There are lawyers who will tell you things like, "Oh, they'd rather settle than bear the expense of a suit." Suuuure they will. Not if THEIR lawyer has told them there is a $100K pot at the end of the rainbow, and definitely not if they have made it into a personal vendetta.
"I mean how much cash they would have to spend for all the necessary procedures?"
I filed a federal suit for a client last month. Total cost - a couple of hundred dollars. Now, I filed that case in Maryland, and the defendant is in Los Angeles. What end of that stick would you like to be on?