I am not going to do the comparison shopping for you, that's your job. MidwayUSA has Black Hills factory-new, 308 caliber ammo with either the 168 gr Sierra MatchKing or the 175 gr Sierra MatchKing (your choice).
Their prices for ammo with the 168 gr bullet are - $15 for a 20 round box and $346 for a 500 round case.
Their prices for ammo with the 175 gr bullet are - $17.50 for a 20 round box and $430 for a 500 round case.
MidwayUSA 308 AmmunitionHaving said all that, by the time you pay for even 500 rounds of factory match ammo you could be set up to reload you own. It's fun to do and I'll bet that by the time you reload 1,000 rounds, I bet you have broken even. Personally, I bought a Dillon progressive press which costs more on the front end, but I can realod 500 rounds of match quality 308 ammo in about 2 hours at a cost of less than $200. If you have brass left over from shooting factory ammo, 500 rounds will cost about $100.
You should look into this. Reloading can save you serious money and becomes a very enjoyable part of the shooting sports.