Coleman's Xtreme line of coolers is one of the best bangs for your buck on the market. They're usually under $100 and can keep ice for up to five days. It's even better when they go on sale.
The Coleman 70qt Xtreme Marine Cooler normally retails for $50 at Walmart, but you can get it for just $40 right now with free two-day shipping. This particular model can hold up to 100 cans and has a lid that doubles as a seat with four drink holders.
I bought a 70qt Xtreme cooler last year and was able to keep ice for a week in the summer heat. So you definitely don't need to spend hundreds of dollars on a cooler for it to be reliable. But what you will be missing is a locking lid, wheels, and additional accessories for the cooler.