A lot of the backpage girls are basically streetwalkers. Especially in D town. Not that that's a bad thing, but it certainly adds a level of risk for you. It's not the safest way to go.
kind of a catch-22 on price. If you know they're good it's because of good reviews and history in the hobby. But if they have that they'll probably charge around 200. Many stick to 300 even though the economy isn't good enough to demand that much for average looking girls doing straight service, IMO.
Up and coming providers with some, but not many reviews and/or "BBWs" are probably your best bet to get a sub-200 deal for an hour. Otherwise just go 1/2 hr with a more expensive gal from a less shady site.