Salsa is of course best freshly made. Besides, as a number of people have mentioned, it is very simple to make. That said, the quality of grocery store tomatoes quite often leave much to be desired. For the past year or so, I've outsourced my basic salsa to Pete's fresh market*. They have a number of salsas, in a refrigerated display opposite (to the right of) the deli. The basic 'salsa' I get is the one labelled pico de gallo and is priced $1.79 (per plastic tub or per lb.) It is a bit watery, but has a wonderful fresh flavor, generously cilantroed, nice heat and keeps well for four to five days (it helps to look for the ones with a later 'packed on' date

).
For the price and the corresponding quality vs. price of tomatoes, it is my choice of salsa. I will mention, FWIW, that prior to discovering this I had generally always made my own. They also have a salsa verde, with tomatillos, which is also good, but I prefer making my own. I first bought their salsa, intrigued by the salsa chile de arbol, a liquid red 'sauce' chock full of the chile seeds. It is very flavorful but has a little too much heat for (my) regular use (but nice, a large spoonful at a time to spice up other cooked dishes - I wish they sold smaller amounts, although this does keep much longer). I also get the tub of sour cream (crema) next to the salsas (can't remember the brand, but it's not the VV Supremo (?)
I'll edit in the right names and brands after my next trip there).
Pete's also sells guacamole, in the deli section - a tub is always kept out for tasting. It is alright, but fresh homemade is much better, given that you can always pick up some fair priced avocados there.
On a totally unrelated note - Pete's has started selling goat (chivo) for some time now @ (iirc) $2.29/lb (not prepackaged). I cannot tell whether it is in fact mutton :?: link
*The 47th/Kedzie location. I have found the quality to be somewhat better and more consistent than the 57th/Kedzie location.
Pete's Fresh Market
4700 S Kedzie,
Chicago, 60632
(773) 523-4600