Some people will not stop looking until told to do so. It doesn't matter whether they've lost a $6 ProV1 or a junk ball. Sometimes these tireless searchers are motivated by not wanting to hurt their score. In other instances, they simply don't want to give up looking. On many occasions they look so long that their group plays ahead and finishes the hole without them.
Others are in the oppositie camp, having no emotional attachment to their lost ball. Most often these individuals buy their golf balls in bulk through some online dealer. They hit a ball into the bush and say "Oh well, that only cost 80 cents". Additionally, while these people care about their score, they often take a more realistic approach to searching. They say things like "That one is in there too far so there is no point in looking" or "I am not getting any wood ticks today".
Both groups are right. Whether you want to search a bit or not, that's up to you. Just remember a couple of things. Firstly, if you think a ball is in trouble, hit a provisional. Secondly, you have three minutes to search. If you find the ball in the bush, you may take a drop within two club lengths of the found ball. And finally, if you can't find your ball and did not hit a provisional, the official rule requires you to go back to the spot of your previous shot and play under stroke and distance. If your local group allows you to simply drop where you think you lost the ball, you must add two strokes.
The last point sometimes causes confusion. For example, you hit off of the sixth tee and think that you are okay but eventually can't find the ball. You can go back and hit three of the tee. However, if you don't return to the tee and drop further up the hole where you think you lost the ball, your next shot is your fourth.
I also believe that there is no such thing as a lost golf ball. Someone will find it. For example, I found a ball last week and showed it to someone. They said "That's mine. I lost it last night". Of course, they extended their hand and I returned it without question. Maybe I should have charged a small finder's fee of something.