I have an old slow cooker with a non-removable "crock". It still works great, so I don't want to get rid of it, but it's kind of a pain to clean. I'd buy those slow cooker liners, but the darned things are $2.79 for a measly 4-pack. Wouldn't take long of buying those before I'd have spent what I'd spend on a whole new cooker. Anybody have a brilliant idea for a more frugal alternative?

Check out the measurements of your cooker, & try at a thrift store to find an asparagus cooker (or maybe a stockpot) with somewhat smaller dimensions.  POSSIBLY, you might be able to find such.  Otherwise, I'd go with the investment in a new slow-cooker, rather than paying for those disposables, so bad for the environment ....

I know this is different advise than you are looking for, but another idea might be to replace yours with a good used one.  I see crock pots all the time at yard sales.  I had my favorite one  for 18 years before it finally died.  It was the metal rectangular pot that sits on an independent heat griddle.  My husband got me a new crock style one for Christmas, but I missed my old one.  The new one quit working after 2 years, and when I went to replace it with the type I had originally had, I found they were $45-$50!  I began to look for them at yard sales and was able to locate the one I wanted very quickly, barely used, for $5.  I also use crock pots to melt candle wax and have purchased two more crock style ones at yard sales in the past year, both for just a few bucks. 

jbettin:

 . I'd buy those slow cooker liners, but the darned things are $2.79 for a measly 4-pack

 A long while ago, I bought a few packs of these, as I had $1 coupons for them.  Only I now forget   to put them in. when using the crock pot.  Thank goodness they don't expire.

 Hi ... I have a few older crocks, too ... to keep food from sticking and aid in easy clean-up, spray crock well with a canned veggie spray or veggie oil on a cloth and this should do the trick. 

Turkey /oven bags make great liners, I tried it a few times and everything stayed in the bag. I try to grab a couple extra boxes at Thanksgiving time when they are mostlikely to be on sale.

according to Reynold site you should not use them

I use cooking spray

and for things like meatloaf I use a foil sling .

I keep reading in recipes to spray the crock with Pam prior to using it.

1. While the crockpot is still hot (empty the cooked food) pour warm water into the pot drop in fabric softner sheet while eating dinner let it get really hot turn to HIGH. whatever is in the softner helps loose the sticked on stuff.
2. I will also use a paste of ( water/baking powder to scrub it will remove stuck on food on anything) w/out scratching.