I'm not sure that what you are looking for is all that expensive. Most full-timers rely on cellular internet service because almost the entire country is covered these days, more and more of it with 4G service which makes possible streaming video and most anything else you would want to do.
Many (most?) full-timer RVers use Verizon because its coverage area is the greatest; it you wanted to have a backup AT&T can provide coverage in a few places Verizon can't. How much data you choose to buy on your monthly plan is your own business. I have a grandfathered unlimited data Verizon plan and like to stream video. We use ~35GB/month.
You can get your cellular internet access by using your smart phone as a hotspot or with a MiFi-type hotspot device. That's really just a matter of preference; they both do exactly the same thing.
(I'm not going to discuss satellite internet, since these days that's only a consideration if you absolutely must be able to get on the internet everywhere.)
To improve your cellular reception I suggest getting a Wilson Sleek 4G/3G amp with magnetic mount antenna. Put your phone or MiFi in the Wilson's cradle and get substantially higher signal strength.
Even though you could connect all the equipment in your RV directly to your hotspot, I suggest getting a "RV-router" and having all your devices connected to it. That way when you get to a campground and want to try out its wifi all you have to do is let the router connect to the new network and everything in your RV will be connected to it. Routers with this capability are made by a number of companies and you can search for them in this forum using terms such as "wifi range extender". You can spend $100-$500 for such a device depending on how much range (distance) you are looking for it to provide.
That's pretty much all you need in order to obtain state-of-the-art high speed internet these days. 4G cellular provides downlink speeds of ~5-15 Mbps which is more than is needed for HD video streaming. The cost issue is how much data you want to pay for, not what equipment you need. You can support a lot more than 3 users with this setup; the network in my RV consists of 2 laptops, an iPad, a Nexus tablet, a Roku, a printer, and a DirecTV DVR!
