Having completed over 4000 events, I'm finding myself more and more discouraged by the increasing ratio of time spent to further progress.  A recent example:  After many weeks of play I had managed to accumulate just over 400G.  Reviewing the record of my progress (I keep a detailed spreadsheet tracking my progress in every series) I noticed that I could purchase the Jag F-type used in the Elite "Coupe de Grace" series for 400G.  There are only 2 cars in the series and with only the Carrera S with a PR of 44, I couldn't get close to 50% completion.  With high hopes I spent the 400G and took delivery of the Jag with 7 upgrades already on it from a previous challange.  Unfortunately I quickly discovered that the 2nd race of Tier 10 required a PR of 53, the 1st race of Tier 11 required 56, and the 2nd race of Tier 11 required 58.  So for my 400G I was only able to get to 48% and couldn't unlock Tier 13.  

When I first started playing this game 1800 hrs ago, I had trouble understanding the level of anger often expressed on this Forum.  Not anymore.  What bugs me more than anything else is the Monkey's refusal to offer any type of "R$ to G" swap. It's clear to any player who's above Level 100 that their accumulated R$ balances are useless.