There's a reason for that increase in hotel room costs on weekends in Vegas. It's close enough to be reached from Los Angeles and San Diego. So folks go to LV for the weekend, leaving on Friday afternoon, and then heading home Sunday afternoon. It fills up the hotels (supply and demand) and clogs the freeway (15).
That one-way fee is usually charged because a car has to eventually go back home (for licensing/registration, fees, eventual sale) and that's how the companies recover their costs for that. We have folks who have told us that they got the fee waived by rentalcars.com, but it may depend on which rental car company.
Lodging costs are higher inside almost every national park, than they are just outside the park. That concession fee, I guess. General rule-of-thumb is, the further you get from the park boundary, the less you'll pay for overnight lodging. But then you'll spend more on fuel. Sometimes you have to compromise.
Donna