It probably doesn't factor in currency conversion (i.e., it's likely based on how many USD are spent and ignores the fact that you're making EUR in Alicante).

Just a thought at least.

The site says Miami is 5% more expensive than San Jose. That's a horrible lie.

Yes, in your interpretation what that data means.

Just a quick glance at craigslist for 1000sq foot rental in San Jose, CA shows that expatistan's "expensive price" is below average. While the Valencia Spain rental price is higher than any I have ever seen personally.

Likewise Spanish food prices are inflated on those sites which you can confirm by looking at mercadona.es which is a mid-high end grocery store in Spain.

But mostly: Valencia and Alicante have huge populations of retired working class British people. There is no way on this earth a retired working class British person could survive in San Jose let alone thrive.