Keep an eye out!

You can sometimes find GREAT DEALS on 1/400 Gundam Collection figures if you keep your eyes peeled!  I was lucky enough to find these at the 2013 New York Comic Con!

Gundam Collection Figures stopped with Volume DX9 in 2010,  so finding them "out in the wild" is like hitting the jack-pot!  There are plenty available on eBay, but a lot of times you are subject to bidding wars; and that can sometimes be a pain.

If there are specific figures you're looking for, you can contact KTakuya2012 on eBay and he will do his best to find what you're looking for and for a fair price.  Please be aware however that he is located in Japan, so shipping prices can be on the steep side - but if it's something that you can't find anywhere, the price might be well worth it.

Right now I'm getting my Gundam Sentinel Collection together and I was able to get an MSA-011 S-Gundam, MSA-011 [Ext] Ex-S Gundam, FA-010 Full Armor ZZ Gundam and MSZ-010 ZZ Gundam for a very reasonable price.  Now that ALL these figures are no longer being produced, they're going to become more scarce.  So I'm sure prices will be going up as time goes on.  I wouldn't exactly call these an "investment", but I'm sure I could eventually sell them in the future for more than what I bought them for.