I've been in my house for ten plus years, and this is my 1st year with A/C. I have a whole house fan. Get it cold overnight, would stay below 80 even during hot days. The biggest factor is insulation and thermal curtains. Reflective film on the windows is a huge help too.

A friend put a modern central evap cooler in a couple years ago and it is SWEET. My house would have been more trouble than it was worth or I'd have done it. If you're basing price on the example you gave........get ready. Prices are bananas.