It turned out the both of my cars had their batteries die within the same week recently, so I was in the market to replace them. The batteries, not the cars.
I called around to various battery stores thinking that a place that specializes in battery is likely to have the best price.
One place that I've bought some batteries from before had the Bosch battery I wanted for 500 soles, which seemed pretty good compared to the 700 that another place wanted for the same battery, and the 1200 (?!?!?) that a friend of mine who used to be a manager at an auto repair shop said they wanted (he couldn't believe it either, but I guess they figure they'll pull in a few suckers every now and then).
But eventually I found the best price at Sodimac of all places. The very same battery was 400 soles there, though I ultimately decided to buy a different brand battery that seemed identical (though made in Columbia instead of South Korea) for 300 soles. I'll give it a try and see if it holds up as well a Bosch.
The bigger surprise was that Sodimac will install the battery for free. This turned out to be important when I brought in my other car which has the battery in a very difficult to access location which requires taking off the wiper blades and removing the cowl first. They had to watch a YouTube video to figure out how to do it, but they persevered for over half an hour and managed to do it successfully. I'm glad I had them do it because it turned out that the battery they had originally suggested wouldn't fit so they had to return it (even though the packaging was already open) and get a different one.
Anyway, this may not come as any surprise to some, but it was to me, so hope this helps someone.