So with the 1.02 beta patch, buyout costs got changed to 10 BC per MP, but upgrade costs weren't changed.  This isn't really important for my observation, but I just wanted to mention it since it is related to this... 'exploit'.

If you buy out a ship, it costs 10 BC per MP.

If you upgrade a ship, it costs 30 BC + 6.6BC for each extra MP worth of upgrade you're doing.

So would you rather design a colony ship, that costs say ~100 MP to build, or 1000 BC to buyout..

OR

Design a colony 'hull' that costs 42 MP to build, and also design a colony ship that costs 100 MP to build.

You buyout the hull for 420 BC.  Next turn you upgrade the hull to a full on colony ship for 30+((100-42) * 6.6) = 412.8 BC.  So you just bought the ship (albeit 1 turn later) for only 832 credits instead of 1000.  

Does it seem strange to anyone else that this is cheaper that building it directly?  This same strategy can be applied to ALL hulls, again you trade a turn of having the ship now for having it cheaper, but you only fall behind by ONE turn, since you're able to pump out a ship every turn and upgrade a ship every turn.