there are a great many different 7mm rifle rounds, Savage chambers at least two: 7mm-08, & 7mm remington magnum. Any 7mm is suitable for deer with the right bullet, generally in the 139-154gr range, & if its a 7mm Magnum its useable on game larger than deer, such as elk & moose with 160-175gr premium bullets like the barnes tsx or trophy bonded.
Ammo price varies tremendously depending on which particular 7mm and whether you buy standard-grade or premium. Bulk ammo can usually be had thru Cabelas & Sportsmans Guide, typically standard-grade hunting ammo which will work fine for deer. That way usually averages out to about a dollar per round, whereas 20-round boxed typically cost $30-$45
Savage 110 is a good rifle, depending on condition could be worth anywhere between $200-400, the scope not really adding value in this case