If I recall correctly, when I subscribed for cable, and received a box, I was fully aware of the cost of a lost/broken cable box. They made sure that you knew.
I'm sure these people were made aware as well.
They're a bunch of welchers.
I agree. $300 is too much for a cable box, even a digital cable box. Here's a twist, does the agreement state the cost of replacing the box? If not, then a reasonable replacement charge should be administered. It sounds as though the company is screwing you both ways, you should be able to buy the box outright (as with satellite companies), or you should be able to rent-to-own the box. I would say that if the subscriber can show they have paid at least 300 bucks worth of rent, no issue. If not, pay the difference.
My wife's (girlfriend at the time) apartment was robbed and they stole her rented caller ID box. The phone company billed her over $50 for it. She said "No way!", and went out and bought the exact same box (brand name and all) at the store for $15 and sent it to them. They had a new box and she saved over $35 on the issue.
Why do they still have boxes (except for digital)? I've lived in several areas that only require you to hook into the coax at the wall, no box. Everything is handled at the source. Even for premium channels.
I agree, though, if the lease says you're responsible, suck it up.