Long term history of DVC: see http://galaxies.mygamesonline.org/digitalisassets.html

The actual plots and pages there are kind of in reverse maybe to what you want, for example the list of what all other things cost in terms of devcoins and the graphical plot of what all other things cost in terms of devcoins, but the raw underlying data would do what you want, basically you just need to pick out the devcoin columns from the lists or plots of all the other assets.