I already had Nat Geo maps for OR and WA (I grew up in OR, live in WA) so when I thru-hiked I just needed to get CA. The Pocket Topo product worked okay on my smartphone; somewhat buggy but did the basics fine.

I'll attempt the AT this year, and for exactly that reason I switched products. In fact, for 14 states you don't have to buy 14 different Nat Geo products as they clump some together in sets like "New England", etc, but it's still quite a lot of money. I switched to www.memory-map.com and got their higher end product that allows import of geotiff maps. Got the geotiffs for free; can also buy all the AT set for $25 on DVD. Found an AT trail trace online and use gpsbabel to convert it to a format that memory-map could load. So some learning curves and effort and money spent, but now I can load maps for anywhere in the country for just some effort. Print them out if desired, or put them on my smartphone (with GPS).

So there are alternatives.