Warning: This post may be longer than you could handle
To clarify one thing, my suggestion wasn't really to lower the price. You would get a discount by doing something; for example racing three months (> 300 races) so people who bought it for 20$ wouldn't feel cheated.
This suggestion wouldn't change the game and is therefor more realistic.
Now to my second suggestion
A bit more unrealistic cause it would require changes to the game but not too much I think.
In the beginning (before my time), you had a 0.xx version which was free and many players were online. Many of them were the type of player who just wanted to have fun and play a few races between this and that. There were tight battles and these players wasn't so interested to join cups etc, just to have fun racing now and then. Then it happpened... the suddenly looked a bit nicer and cost 20$ - most of them left. Why?... Maybe they thought that graphics and mods wasn't all and the possibility to meet the new exiting players and share a few casual races each night would diminish.
How to get some of these back
If you though that TS is a fun way of killing time but you didn't want it to be too serious then price is a factor.
What if you could get this kind of racing game for say 10$, then there would probably be more impulse-purchase of this game and you wouldn't need those who would go weeks of playing demo to decide if they would pay 20$ or get a few beers downtown.
My proposed solution
Strip all mods of TS and just deliver a racing game for 10$.
Then for those who like there would be upgrades for this game.
Punaball +5$, BattleMode +5$ (both of these upgrades would unlock the modding capability of this game)
For those of you who discussed freeware. Another suggestion would ge to have a basic racing game as freeware and then provide upgrades for a small amount.
PS. I know that changing the game isn't most likely going to happen so do not comment on how improbable that would be, instead comment on the idea itself please.