There is a company out there called Get Unlimited which is offering to rent a Nighthawk for 89.99.

https://www.getunlimited.net/plans

The 89.99 includes the device rental (normally 250 dollars) and unlimited, unthrottled data.

While it's not the most economical to also have to rent the device you wont have to pay the restocking fee that you normally would if you by a hotspot and dont like its performance.

If you already have an AT&T hotspot you could do a SIM only plan for 69.99.

How does it stack up to Comcast? Their mid range plan is $92 dollars everyday price and with the modem rental is about 110. The nighthawk plan pricing is comparable to a low end Comcast plan but it's a 1GB device.

If you are in an urban area with a lot AT&T circuits I can see fairly easily 100mbps.