Many of the small city parks and fairgrounds in Nebraska, Iowa, and Indiana allow camping, or at least don't run you off.
Also, if you ask maintenance workers in the parks, or the local police, they can tell you what is available. I think this approach seems to work better if you are not on a main ACA route where hundreds of cyclist pass through monthly.
In Oregon Hiker/ biker sites are usually $5, which is a pretty good deal, and should not break the bank. On a tour earlier this summer, three of us stayed stayed twice in National Forest campgrounds for $3.50 (total) a night. I have a "Golden Age" passport that gets me into Federal parks for free, and campgrounds for 1/2 price. However, the price for getting one is steep; you have to get old.
The county fairgrounds in Lusk, NE. We did not ask but just pitched our tent out in plain sight. Some of the locals invited us to a horse show taking place there later in the evening. By the start of the show the whole town knew we were "stealth" camping. There was a city park nearby, but we were warned that the sprinklers came on about 11:30 pm.
