Economic sense? No. They put low fares into place to encourage ridership. In terms of PR it might make sense to grab all of the equipment they can and run it, but the odds of a sold-out train covering its costs at $3/5 per seat are pretty low (revenue per run would run somewhere in the range of $850-950, depending on whether there's any significant turnover at FLL; 48 Select seats and 198 Smart seats filled at $5 and $3, respectively, provides $834 in revenue), though it would probably still be at least passable cost recovery. After taking the NARP discount, I paid a whopping $9 round-trip in Select WPB-MIA (which is, in terms of cost-per-mile, one of the cheapest train tickets I've ever purchased...I'm used to yields in the range of $0.20-0.50 in coach, $0.40-1.00 in Business, or $1.00-2.00 in First on the Acela, and this shakes out to about $0.065/mile in Business).
Don't forget, on opening day in January they were charging $15 in Select and $10 in Smart for one way WPB-FLL, so they knocked the fares by 2/3 for Miami's opening day.
Right now, I'm showing Select sold out southbound on every single train FLL-MIA. Smart is sold out until the 1820 departure from FLL. The 1742 departure, as of this writing, has six seats available. The 1942 has about a third of its Smart seats left (I think I counted 85 available). 2142 only has about 25 seats taken (so something like 170 seats available).
Between WPB and FLL, Select is sold out on three trains (1100, 1300, and 1900). 0700 shows 24 Select seats available, 0900 shows 16 Select seats available, 1500 shows 10 Select seats available, 1700 shows 10 Select seats available, and 1900 shows 10 Select seats available.
Northbound, Select is also sold out MIA-FLL. There's Smart space available on the 0910 (69 seats), 1110 (26 seats), 2110 (62 seats), and 2310 (50 taken, so 148 available).
FLL-WPB, the first three departures are sold out in Select. 1545 shows 10 seats available, 1745 shows 10 seats available, 1945 shows 21 seats available, 2145 shows 23 seats available, and 2345 shows 39 seats available. NB that these are all on trains where MIA-FLL is sold out.
There are no trains showing Smart sold out FLL-WPB, though in a few cases the pickings are getting slim.
Please note that this is getting pretty high up in terms of load factors: Select is at 100% FLL-MIA/MIA-FLL, 81.8% WPB-FLL, and 73.1% FLL-WPB. In terms of raw load factor (and presuming 44 miles WPB-FLL and 26 miles FLL-MIA), Select is at 85.8% (46,148 seat-miles are filled out of a potential 53,760 seat-miles). FWIW I don't see this going much higher, given that you're effectively getting a lot of FLL-MIA tickets blocking out WPB-MIA sales as well as sold-out trains one way blocking a possible round-trip. Overall, you have
71.2% 85.6% of all available seats into Miami sold out four days out...and of the 566 available seats, 318 are on the late-night round trip and another 69 are on that first train out (which I'm on only because I need to be back in Dunnellon ASAP...otherwise, yes, I would've probably booked at least one more round trip over the course of the weekend).
However...this is only for Saturday. Sunday is looking not-that-far-off, however: Several trains are already sold out all the way through, though there are also still 11 Select seats available on the 0700 WPB-MIA.
Edit: Something else to bear in mind is that, given the lack of finished crossovers and the like, shoving another set (or two) into service might come close to shutting the FEC down. However, putting that equipment into service might also (ironically) sell some more tickets on the later existing trains...one thing quite possibly hurting the late trains' load factors is the fact that you can't get in or out of Miami for a good chunk of the day now (though some "joyriders" might be nudged into those odd hours by the fact that you can only get a seat then).
Edit 2: I found this:
https://www.fitchratings.com/site/pr/1032927
So, let's compare notes here. As of a few weeks ago, per the newspapers, ridership was aiming for about 400,000/yr strictly on WPB-FLL. Brightline is projecting 1.1m in 2018 while Fitch put together a less rosy possible scenario of 587,000 for their base case and 907,000 for their "rating case". On the basis of the WPB-FLL ridership, I think it is safe to say that the rating case is probably on the lower edge of what is likely (presuming they can bump some of the midday frequencies back into the mix) with Brightline's numbers on the high side. I'm comfortable that we won't end up in the base case scenario.
Edit 3: Another observation worth considering is that even at the deep-discount fares, revenue for the weekend should be up on last weekend. Going from, say, 25% of seats filled at $15/10 to 85-90% filled at $5/3 still puts you ahead.
Edit 4: So, the cases that Fitch examined all made
ridership assumptions. None of them made
pricing assumptions aside from what Brightline put out. I do wonder if Brightline might not end up making the ridership targets, but be stuck with modestly lower pricing until the Orlando segment opens up.