Just got back from a week there. Stayed at the Big Bend Resort RV Park. Think I paid about $25 a night for 30A & water in the no reservation section. Since it was Thanksgiving school break, everything else was booked.
As far as the park, it was pretty much to be expected for the area, dirt roads but out of all the parks I drove by, they did seem to be the largest with the most amount of shade trees, which is a rarity in that area. Nothing like shade trees from mountains like Colorado, Montana, etc...just West Texas desert shading. They do advertise WiFi, but from where I was located in proximity to the office, it was pretty useless. The do have a lobby/TV/pool table kinda area that you can chill at and the reception is much better. Showers are $2.00 for 5 minutes and it's well worth it after a long day. They also have bathrooms, but can get congested at times. they do have a laundry facility from 9a-5p that has a bathroom as well...USE THAT ONE. Minimal traffic. Overall, I was happy with the location and overall campground itself, and I wouldn't have a problem staying there again, but I'd plan better and make reservations.
Price for diesel was $3.30/gal & 2.95 for unleaded. There are visitors centers withing the parks that sell fuel, but didn't check prices. With the exception of beer, everything is about 25-35% higher there that what I'm use to paying at home. The closest Wal-Mart was about 150 miles, so take what you think you'd need.
As for Big Bend, you really have to experience it to understand it and become infected with it. It's either love it/hate it. If you're use to having activities overload on trips, then you might be disappointed. However, if you're willing to seek out the beauty of the area, then it's easily to get overwhelmed with the geology/ecology of the area. There are several miles of dirt roads to travel (4x4, dirt bike, ATV) and several hiking trails and that's where you can get a true feel for the area.
Terlingua is a quirky town that has a personality that can't really be described with just one word.
Fall & Spring are their buzy seasons so plan ahead with the holidays being even busier. Overall, it was a great trip and it will be on my to visit list again real soon.