You need to factor in the personal value to you of the 10 aircraft and airports you pick up. Basically which ones will you actually fly or go to and what they are worth.
Also not all 1st party planes are the same price. For example the AN225 is worth a lot more than say the c195.
The decision is a lot easier for new purchasers of the game and the price difference is a lot less. Upgrading once you already own the game is expensive.