Wang Ka, what does being collectible have to do with refunds? 
The way it was put to me was “The customer has the right to have any reasonable request granted.” Losing money on a transaction is not reasonable unless something really unhappy occurs. Depending on the scale of the business and or the product/service involved you might be able to write off a chunk of a transaction to appease a customer. The kinds of “appeasement” I see in my job frightens me sometimes, but considering what we pay for our product I know we can afford it most of the time.
Why do I get the feeling the OP’s role model is Jack Black, in “High Fidelity”?
Oh I know, it’s entirely possible the OP is a swell guy who just has hundreds of idiotic customers, but somehow I doubt it. I say that because I run into his kind here in Austin, everywhere I go. “Service” industries in Austin are FILLED with people who THINK they should be rock stars or acclaimed filmmakers, and are furious that, instead, they’re working at minimum wage jobs where they have to serve people who aren’t NEARLY as cool as they are.
When I’m a customer at ANY shop or restaurant, I won’t say I’m always “right,” but I’d say I’m polite and fairly reasonable. And when I ask an employee for basic assistance (“where do I find this-or that?”), I think a simple answer without any smirks or sarcasm would be nice.
Here in Austin, of course, that’s often too much to ask for. Ask a clerk at Tower records where to find a CD by your favorite artist, and you’re liable to hear a lecture about why your favorite artist sucks. (Pssst- hey kid, you’re not a music critic, you’re a sales clerk! Get over yourself! NOBODY is saying you have to listen to the CD I want! All you have to do is point me to the aisle where I can find it!)
For that matter, I’ve gone to local delis where the sandwich makers smirk if they don’t think the toppings you order on your sandwich are cool enough. (Pssst- jerk! YOU don’t have to eat my sandwich. All you have to do is make it the way I ask for it! Instead, you blow me attitude, and then wonder why your tip jar is empty.)
I don’t KNOW that the OP is the same kind of person, but I’d be willing to bet a quarter he is. I STRONGLY doubt whether customers walk in off the street and pick silly fights with him. More likely, they come in and ask for comics he thinks he’s too cool to sell, and gives them some serious attitude.
Sounds like someone got kicked out of the hipster pool, and now he wants to pee in it. And besides, who shops at Tower, anyway? Sound Exchange is waaay cooler. 
It’s hard to get kicked out of someplace you’ve never been! I wasn’t cool when I was in college, and strongly doubt that I’ve gotten cooler in the meantime.
But that really isn’t the point, is it? If you’re a sales clerk at Tower, you’re no better or worse than a sales clerk at HEB or Randall’s (grocery chains, for those outside Texas). If I ask a clerk at HEB where they keep… oh, for the heck of it, the Pop Tarts, I’ll never hear a lecture about why Pop Tarts are no good. Somehow, the kids working at HEB understand that it’s their job to sell the customer what he wants, and it’s no skin off their nose if I choose to eat something they don’t like.
The way I figure it, if I buy a Kenny G or Partridge Family CD at Tower (I never have, I’m just pickingtwo random, un-hip artists), the clerk is free to laugh hysterically as soon as I’m out the door. Until then, a little basic courtesy is in order.
As one local DJ likes to remind snooty slacker waiters and sales clerks:
YOU didn’t cook the food, you just SERVE the food.
YOU didn’t make the records. You just SELL the records.
YOU didn’t write the books, you just SELL the books.
And to the OP… YOU didn’t draw the comics, you just SELL comics.
I know, I know, everyone’s a critic. But some people like it that way, believe it or not, which is why places like Tower and Sound Exchange still exist in the face of Wal-Mart and Best Buy. Austin is worse than most, but you’re still plenty able to vote with your dollars. Plus, there’s nothing in the rules that says you can’t play their game, too. Tell them that their indie high ground is pretty shaky, considering they’re just regurgitating what they read in the Austin Chronicle. If you don’t care what they think, then you don’t care what they think.
In another window, I’ve actually been reading a piece on Salon that is semi-relevant. And while I’m not claiming the OP is on par with professional movie critics, it raises an interesting point. Without critics, there is no one to offer a viewpoint that competes with the manufacturer’s advertising. And even if you don’t agree with a “critic,” you can usually use what he/she says to further your understanding. If the clerk thinks that album sucks, ask him what else sucks in a similar way. Now you got tips on what else to buy. The clerk doesn’t actually hate you, he just wants to engage with somebody at his boring-ass job. It may be misguided, but it can only bother you if you let it.
Astorian–thank you!
The phrase “The Customer is always right” is a business slogan not a life philosophy. It worked for H. Gordon Selfridge and a whole lot of people but it isnt the only slogan in town. If your product is good, people come to buy that. You only decrease the ‘return customers’ by being rude and most successful business consider the ‘return customer’ the most valued customer. If youre fine with the the one shop volume of customers, hey, cuss the lil nerds out. If youre thinking of expanding into a chain of stores statewide, then your attitude has got to go.