I have to disagree with author regarding the B30. It really should have a fare that high as it's a premium service that is more expensive as it will have less riders per mile than an intra-city route.

I would put a few caveats on that recommendation. First, WMATA should put a cap on the TOTAL fare paid if you use the B30. For example, if you go from somewhere in DC to Greenbelt on the metro then to BWI on the B30 the total fare should cap a say 8 dollars. Second, the buses should be more frequent, say every 10 minutes. Third, they should have luggage racks. Fourth, service should late match the Metro hours. Fifth, there should be SIGNIFICANT upsizing of the service on holiday weekends, etc.

Finally, airport employees/airline employees should be eligible for some sort of commuter rate.

Frankly, this type of route just screams for a Public/Private partnership since it's outside of WMATA core competency. A contractor could invest the required capital in bigger buses with luggage racks, low floors, etc. Give them the ability to charge a premium fare and they can make this work while providing a high quality service to riders.

The B30 is a great bus, but it needs to be advertised so people in Baltimore know they have an option of getting to DC and vice versa on weekends or during the daily MARC breakdown.
I'd personally like to see the MTA take over the route and have it stop at North Linthicum & BWI instead of BWI Business District. From North Linthicum the light rail runs twice as often to Baltimore, so it makes that connection a little faster.
With a North Linthicum vs. BWI Business stop and 20 minute (rather than 40) intervals, I'd eencourage friends from DC to take that rather than MARC during the week if they are going downtown as it would be easier to get to Baltimore and just as fast.

$6 for the B30 is just as bad as $3. Not because the price is too high. Rather, because another odd number is simply going to cause ridiculous delays as tourists and other people fresh off a flight hold up the line (and thus, the bus) looking for dollar bills. I think that simply charging $5 is the way to go. It's still charging a premium rate for a premium service, but this allows for the bus to be boarded faster. The fareboxes can already accept a five, so why not go this route?

Alternately, some kind of pre-payment system would be great and solve all these issues. Similar to how you can buy single ride tickets on Light Rail/Metro Subway, you could set up a machine to buy a single ride ticket for the B30, and just hand it to the bus operator when the bus arrives. Let the machine accept credit/debit also, and that solves just about every problem with payment on that bus.

(of course, that doesn't fix the problem of that bus needing to come way more frequently than every 40 minutes, but we know that already)