Under the $500 mark.

I'm looking to upgrade, but saying, yeah, this one or that one that are $1600 - $3000 is just rediculous. LOL How about for a man on a budget. I mean, dang, I only give $4000 for my boat, spending half the cost of the boat on a depth finder is just not in my resources.

So for the man on a budget, not looking for side imaging, what is the best old school technology, fish finder? GPS is a plus, but not a must.