Originally Posted by DCAorBust

You're welcome. September is hurricane season so you're going to have some deals, and SJU is such a saturated market that the fares are often low to begin with.

I used ITA. If you're familiar with the advanced routing language, it's pretty easy to plug LGA,BOS into various combinations of a routing to see what works and what doesn't in order to rope in a shuttle segment. Sometimes it works better on the back end than the front end, etc. Then use the multicity engine on Expedia or similar to verify that you can actually book it.

I suspect that you could add trip insurance for another 20 bucks or so and get some sort of refund if there's a tropical storm.