Solid/affordable sniper, that isn't a piece of crap = Classic Army (CA) M24. Comes in around $350 - $400. Worth while sniper rifles go up in price from there and all will likely need some upgrading/modification.
Grab a G&G M4 as an ol' reliable backup at around $200.
Before going all sniper, read this;
http://www.airsoftcanada.com/showthread.php?t=158804