I tried investigating the problem. At first, I thought this has to be something wrong with the repository. So i changed the repo to a different mirror. Even on the nearest mirror to my country, the connection still looks shitty. Never mind, let's try another one. Still not working. The day goes on and finally i ended up trying 5 different mirrors with no luck. Holy crap, i said to myself, this has to be something i overlooked. I changed the DNS to Google public DNS too but still, that didn't make anything better.
I opened up Iceweasel (a Firefox clone that is preinstalled in Kali - Firefox can't be included for some licensing issue they said) and try to run speed test by going to speedtest.net. Oh crap, I don't even have Flash plugin installed. Should I install it? Hell no, I won't do that. Flash is dead. Killed by series of non-stop emerging vulnerabilities. I should download Chrome and observe the speed test using it.
While downloading Google Chrome deb file, i noticed that the download speed won't go pass 40 KB/s. WHATT?? And now I am sure that this has something to do with my connection speed. So, I try to download some random stuff using my Chrome in Mac OS X and there it is. THE DOWNLOAD SPEED IS FINE! ~500 KB/s as usual.
Now I know that my Internet connection speed is fine and Kali Linux repos mirrors are fine, but something is capping my bandwidth in Kali Linux. Is it Parallels? So I shut down the virtual machine and checked the settings. There it is. After changing some setting in Network section, my capped connection speed problem solved. Because I don't find the solution via googling around, I posted the solution here.
PS: I've tried playing around with the settings a bit and i found that changing the type to bridged, wi-fi and so on doesn't matter. The only problem is NIC Type and you have to choose that right.