My Raymarine A65 was $300, plus I had to buy the DSM25(sounder) and P58(ducer) to activate the fishfinder part of the A65, which is also a GPS/chartplotter. The sounder/ducer I bought as a package for $420, so I have a bit more than $700 wrapped up in it.
If you already have the other features covered, it would make sense to get something cheaper though.