Forza Horizon was fun, but I have no interest in the car packs. I had the 1000 GS within the first week. I am near complete again after buying the rally pack (need to win 10 races for the last two achievements but can't seem to find enough people playing the rally portion). I bought the collectors edition, but had buyers remorse once I received it and it came with nothing. Pathetic packaging and benefits. I wasn't expecting Forza 5 with this game, but there is little replay value at this point as I have nothing to work towards. I ended up going back to Forza 4 to try to finish that.
The $10 price range is perfect for the game. Even $20 would be reasonable. My disappointment with the game came mostly at the lack of new cars for the game. Most of the cars are just brought over from 4, where I have already spent a fortune buying all of that DLC. It's a shame they don't let you just transfer that and come up with new DLC cars. Plenty of cars to choose from over the years to find it necessary to rerelease a Jeep Wrangler.