Here are my favourite throwing knives (mass products, as you asked for affordable ones):
Perfect Balance Thrower by ColdSteel
Quite some heft with 430g, but still won't let you end up with sore muscles. Sticks great, my natural distance is right at 3,00m (perfect for competitions). Plus, it's quite sturdy, apart from the occasional blade-dent (-> file repair) nothing to complain.
Hibben Generation I
The first gens are available everywhere for cheap, and throw well. Get the heaviest ones in the shop. The curved handle is a little annoying, but makes you take extra care in release.
Circus Faka
Designed in Sao Paolo/Brasil for knife throwing circus artists. Handmade look, straight design, smooth release. Very sturdy tip! My favourites at the moment.
Gyro Dart by Seberland
Ok, so this is not a normal throwing knive, but a mini spear. But, even a beginner can take this thing and have sticks in 20 Minutes! (The tip is always facing the target, so it's only a question to hit the wood - aiming needs some work.)
@Bobby: Sorry for posting links in my original post, didn't know about the policy.