With respect to signing a starting pitcher, the main considerations for me are value and risk (which mainly relates to the length of the contract). Is Price at an AAV of 30M over seven years a better value than Leake at an AAV of 12M over three years.
Leake won't sign for anywhere close to $36M. MLBTR seems to have him pegged at 5/75, with some guys taking the over, and some the under. Leake also said he wants to sign quickly, so that makes it pretty hard to wait him out and get a good value at the end of the offseason.
I'm guessing the Braves will end up with Lackey on a 2 year deal plus an option. Something like $8M per year for 2 years plus an option with a $2M buyout. That seems to fit the 10/10/10 budget for this offseason ($10M for the BP, $10M for the rotation, $10M for C/LF).