This is from a Leupold Mark 4 spotter those are 4" pigeons at 620 yards. Cheap glass may work good out to 100 yards-- but beyond that you'll want better glass and better coating.
Also check out Nikon-- they make great glass and their warranty is second to none. I have a Fieldscope III that fell off the back of a truck and was ran over by a ATV-- Nikon replaced it no questions asked--- it didn't cost me a penny. The only problem is they don't make it with mils.