"Free" is usually worth what you pay. Get a good GPS
(one that shows just lat/long is all you need), current paper charts
(and learn how to use them) and a good depth sounder. Electronics break down, often at the worst possible time. Yes, chart programs are expensive and it also costs to keep them current. Creating the program and keeping it current is expensive and the programmer needs to be compensated. How much would a hole in your boat cost?