It very hard to tell if it will increase or not, in my opinion I would have to say it will raise. If you can tell RuneScape is currently going through a economic breakdown, from what I can see items are crashing and items are raising at a crazy rate (ex: the dragon chainbody, dragon platebody, etc... other dragon armours are starting to crash and as you can see many people are trying to buy it but no one is selling my guess is these items are going to sky rocket in price as for the high demand as no one is selling. An example for a current sky rocketing price is the full dharok barrows set. Just not too long ago it was 4 million but out of nowhere it went all the way up to 5 million and as you look around on RuneScape you see so many people selling dharok at the lowest price because they know that it will crash very soon) Well back to your question, Bandos Chestplate - a good investment? Currently I wouldnt know for sure, but I say most items that are currently crashing are going are going to out of nowhere sky rocket soon, so yeah it is somewhat a good investment. The reason I say it is somewhat a good investment is because what I think is that most of the items about 10 million and more that are crashing (Bandos Chestplate, Tassest, etc...) will go up, but no by that much. Hope I helped :