Wrong scaling on retina display

I’ve got a problem with client’s project. He asked me to make a website with retina support, so I started doing it with sage 8 (as usual). But on macbook with retina the website looks bigger then it should. I thought that I could break something during developing. But when I looked at my older websites created with sage on retina monitor - there all has the same problem
To make it clear here is some screenshots:
https://1drv.ms/i/s!Al7CIPPT65cjhflMavuL8zFnGW-UZA - this is screen of psd layout, it is showing that website’s width is 1500px
https://1drv.ms/i/s!Al7CIPPT65cjhflDD8Ee6x5xYI0LLQ - this is screnshot from browser (resolution is 2880x1800, but the website’s width is almost the same! No zooming, just normal view. And all other random websites - for ex. some premium themes from themeforest - looks just normal, but not this one!(((
I really don’t know what to do and client advises me to choose some other starter theme, but not sage

Anyone could help me? Or is this a bug?