a few years ago (on my previous C class) I needed new tires due to age. I shopped around including online. Ended up getting a set of 6, shipped to the house for under $500 from tires-easy.com. Took them to the local used tire guy and he mounted & balanced them all for $120. The brand was "Go Form". My opinion, they were descent tires, handled well on the road and not noisy.
It was a smaller C class (26.5 ft) with no slides so the weight was well within the designed weight limit of the tires.
On my current C class (32.5ft, 2 slides) which is much heavier, I don't know if I'd go with "less expensive" tires.
There are many options, especially if you're not in a hurry.
One thing to keep in mind, getting a really good price - especially online - usually means they've been sitting on the shelf at least a year, maybe 2. I replace my RV tires by 6 years from date of manufacture no matter what the tread depth.