Unless you live very close to these Logan Express locations, travel solo, or are traveling for several days, I don't see this being a huge advantage in terms of time or cost. I live about 12 minutes from the Framingham Logan Express. If my wife and I want to take it for a weekend trip, we need to Uber to the Logan Express (around $20 with tip, depending on demand). Then we need to pay $36 for two round trip Logan Express tickets. We are now in for $56 with the Uber. Then add $7 per day for parking and we are up to $70.
Well, if you Uber, you wouldn't need to park? So it'd be $56 for three days (or $57 if you just drove to Logan Express) versus $111 if you use the economy garage, plus the gas and the Pike tolls.