I am interested in doing the TransAmerica Route in 2016. I have a Trek FX 7.5 with 48/36/26 and 11/26 gearing - I think that should get me by ok. I have a rear rack and small panniers large enough for 20 lbs.
It sounds like you already have most of the gear necessary for a loaded tour. The bike should work fine. Change the inner chainring to a smaller one and maybe put a larger cassette on the rear wheel. Easy to do. That will get you low enough gearing for any mountain or hill, loaded or unloaded. I don't recommend it, but you can use just a rear rack and rear panniers. You already have them. You could also figure out a way to attach a front rack to your bike if you want front panniers too. Easy. Cheap Nashbar panniers work just fine. You do not have to spend much money on racks or panniers, or anything else. Other than some camping stuff, you already own everything you need for a loaded tour.
Regarding motel costs. They are unbelievably expensive in the USA. Everywhere they are expensive. I seriously doubt you could find any room for less than $50 anywhere in the USA. Once a year I ride in rural Iowa and stay at motels for a couple nights. $60-70 is what they cost. One might assume, incorrectly, that a rural town in farmland in the middle of the week would be somewhat cheap. HaHaHa. All motels everywhere in the USA are expensive at all times.