Board Thread:Game Discussion/@comment-28568987-20160527163439/@comment-26829117-20160527180452

Also you might want to check out this page if you haven't found it already that tells you which car is cheapest to upgrade for 100% completion. If you are heading that way it will save you a lot of gold in the long run.

http://rr3.wikia.com/wiki/RR3_Wiki:Upgrades_Strategy_For_100%25_Completion