We have a small inground and it doesn't cost us anywhere near $1000 a year to maintain. Like Deana, I just buy a large bucket of tabs and I also buy a bucket of granular shock and that does a full season (March-October); it's not "swimmable" that full time because of temp, but we uncover early and get the chemicals circulating to head off algae. I use about 12# of baking soda at opening to balance the water, spend around $15 on stabilizer, and about $30 on algaecide to close it down. We open and close it ourselves, but we have a flow-thru safety cover which fastens to the concrete with steel anchors and looks like a large trampoline when it's on; that makes it easier than having to pump standing water off a solid cover. The filter does run our power bill up around $20/month, though, so that's another expense.
Ours was installed in 1991, so a lot of the original equipment is starting to go now; I've already replaced the filter, pump motor and chlorinator for about $500 total and we will need a new vinyl liner within the next couple of years and that's a big expense. They told us at the beginning that the life expectancy of a liner is around 10 years and we've already gotten nearly twice that, so I guess we're due. Our concrete has a few cracks and needs a good cleaning. Overall, it's worth it for us because the grandkids enjoy it, but I probably wouldn't put another one in if we ever move.