This has come up a lot and here is my impression for North America at least:

• $10/day and under This is homeless style frugal. Eating beans and rice, possibly suplimented with dumpster diving, and camping in the woods.
• $20/day Pretty frugal, not a lot of money for restaurants or camping fees. No motel days.
• $30/day Seems to be somewhere about average. You usually pay a few bucks for camping, mostly cook your on meals or eat at cheap restaurants. Maybe a motel day if the weather is bad. Room for some snacks at the gas station when you get the munchies.
• $40/day Now you're living. Budget can go to daily restaurants or higher camping fees at private camp grounds or more motel nights.
• $50/day Basically just going along not worrying much about money, eating wherever you want, some motels but still camping most nights.
• $100/day and up You are staying in a decent hotel every night and may possibly be paying a guide or SAG van service or both, maybe even a rider to draft behind.

I take a simple approach to my trip. I divide my projected total budget by the number of planned days out and come up with my overall daily costs. Some days will be more than others, as long as I make a serious effort to stay below my planned daily costs, I'm good.

Next trip: TransAm (Yorktown, VA to Florence, OR), then down the Pacific route to San Francisco. Number of days planned: 101 days. Total budget on hand and ready to spend: $4,300. I arrived at this amount by individual costs for ACA self contained (but guided) TransAm tours. Granted their costs no are more than when I first began my trip budget… but I don’t have to pay the guide. Average daily costs: $42...seems well within my tour budget, especially in light that about half of my nights will be at minimal costs due to City Parks, Fire Stations, Churches, and Warm Showers. A majority of the second half is camping. On average we're looking to motel stay about once a week...motel costs are minimized due to there being at least three of us sharing motel costs.

With the major exception of most breakfasts, we're cooking the majority of our other meals. We tested this out during RAGBRAI self-contained. It worked well, and I was way under budget food wise...I spent $150 on the RAGBRAI registration...so I can say that took care of my lodging for seven days which I do not expect to pay for at least half of my TransAm trip.

FWIW, In my experience those two routes tend to be pretty inexpensive for camping/lodging. On the TA we managed to stay for free a substantial portion of the time and for cheap a good bit as well. In much of the country the town parks were OK to camp in and free. There also were quite a few established places that offered hospitality. On your planned section of the coast you can typically stay in hiker biker sites the whole way at $5 or $6 per person depending on the park at least that was my experience. Hopefully budget cuts in California won't ruin that.

Food was pretty reasonable for the majority of the TA as well. The Pacific Coast was kind of pricey in that regard in some places and not bad in others.

I read something concerning the cuts in the California budget, and where it might impact my trip down the coast. Seems only one area that I had previously planned to utilize got cut...that being the Samuel Taylor SP, north of SF.

Almost the whole first half of my TransAm is at free to minimal costs, then that slims down a little about mid way across Colorado. Fifty-one nights out of 101 are free or donation type stops. I can make that even more with more research with Warmshowers.

Wow! Do you actually plan your stops in advance for the whole trip?

I plan a couple days ahead only where logistics make that necessary. Most of the time I ride to the first available campsite after the 30-40 mile or so point and then decide whether I want to continue. I am often unsure where I will stay right up until I roll into camp. I usually do look ahead to know what my choices are distance wise for the day and if the next day has a big gap in services that might favor a long or short day.

BTW, I usually avoid RV parks, KOAs, and pretty much any private campgrounds like the plague, but on the Pacific Coast I stayed in one KOA that had a reasonable hiker biker rate ($9) and really nice features like pool, hot tub, laundry, outdoor kitchen, and so on. I wonder if there are other KOA like that on the coast. I think that was at Manchester Beach, where the state park was closed. The maps did not indicate the closure.