A printer that does 13"x19"can do a topo map spread over 2 sheets (2x1 poster printing). Whereas a 8.5x11 takes a 3x3 (9 sheets) for roughly the same size map. Who wants to tape 9 sheets together?
The government allows downloading all topo maps in pdf files (as we all know). And printing your own is cheaper than buying them, by far!
The Canon ix6500 printer will do 13x19 and costs under $100 from time to time online. Such as a Staples online (free shipping). I have recently bought this printer and it works extremely well, am very happy. Amazon customer reviews also gives ix6500 high satisfaction (which is rare for any ink jet printer).
The only place I know to get reasonably priced 13x19 paper is paperworks online. 750 sheets of 13x19 is $43 (24 pound weight), they also have it in 20 pound and 28 pound (28 pound is the limit on this printer for "document paper" (copier type paper).http://paperworks.com/store/products/paperworks-document-paper-13x19-24lb-725pkg
In 1x2 printing (two 13x19 taped together to make 26 x 19) will give a 32" diagonal map, about 3 feet, perfect size. And just fold the map first along that one tape line.
I really love this printer! No other one that does such a large format is anywhere near as inexpensive. A great all around inkjet printer.
Much better than even 11x17 for topo maps!