I did the math once and joined up because they had a pile of CDs I wanted and it worked out (even with their ripoff S&H fees) to be about $5 per disc, which I considered reasonable. It was the usual "buy 12 CDs for $1, then buy 6 at regular price within 3 years" thing, where "regular price" was some insane bullshit like $18-$20 each. So 12 CDs dutifully arrived a couple weeks later (and they didn't even screw up the order).
When the "real" catalog came after the initial purchase (the "join-up" catalog was a small subset of their real catalog), they included an insert announcing a 2-for-1 sale. Buy a disc at regular price, get another free. That made the math even better, so I promptly ordered 12 discs (the six to satisfy "the contract," plus the six freebies). And yes, the S&H was still ridiculous.
Then when the package arrived with my order, it was much bigger and much heavier than you'd expect for 12 CDs. And the reason it was so is that they fucked up hard and shipped me three or four copies of each disc instead. Whoops. Mind you, the packing slip had the correct counts and they only ever charged my card the expected amount. They also included a "congratulations!" letter saying I'd satisfied "the contract" and "the deal" was concluded.
It's a little-known, seldom-mentioned fact that (in the United States at least) if you ship something to somebody unsolicited, even if they sign for it, they're not legally on the hook to pay you for it and if you want it back, you can go fuck yourself. The "unsolicited" part is important -- you can't just order $50k of shit from some electronics vendor on a net-30 account and say "lol I didn't order that, but I'm keeping it!" It has to be legitimately unsolicited. As in "I have no fucking idea why you sent me this."
Originally that law (I forget now what it was called, but it was originally a postal regulation that I think got expanded to cover pretty much all consumer shipping) was put in place to stop a then-common scam -- send some poor schmuck some worthless garbage that costs you next to nothing but you list in some catalog nobody ever buys from for ridiculous prices, then send them a bill demanding thousands of dollars for it. After all, you've got the stuff, so you better pay for it. And usually it was bulky enough that shipping it back was a ripoff and a pain in the ass, and often the scammer wouldn't even offer to accept a return anyway. So a law was passed to knock that shit off.
So in my case, all the paperwork said we'd agreed to one copy of each disc. It's what was on the invoice and the packing slip. It matched what they charged my card. The fuckup in sending a bunch of extra copies was theirs, not mine. So I kept the damned things and never said a word to them.
Amazingly, about a month later they actually tried to pull that same scam by sending a fucking bill for the extra copies of the discs they sent by accident, with a quiet blurb at the bottom that in lieu of payment I could ship the extras back to them (at my expense) and they'd magnanimously "forgive me." Instead, I wrote a polite but firm letter back to them citing the law I mentioned to explain why I wouldn't be paying for the extra discs or sending them back.
Another month passed and a letter arrived from them harshly advising me that I was an awful, horrible human being for taking advantage of a poor, defenseless media conglomerate by hiding behind some gay ass consumer protection law, and it was only owing to their own goodwill and benevolence (and -- they begrudgingly acknowledged -- they couldn't actually do jack fucking shit about it) that they were writing the whole thing off and "considered the matter closed." Of course my "membership" was canceled effective immediately. Oh darn.
That letter was amazing though and I really wish I'd kept it. The seething was real.