Boulderboy, I'm not optimistic, and the prices for SJU - VIJ are likely to remain high due to a confluence of factors, first and foremost being a severe pilot shortage that started with layoffs and retirements due to COVID. Here's a pretty good article on the issue: https://www.cnn.com/2023/04/19/business/pilot-shortage-retirement-tsunami/index.html.
After COVID abated, major airlines that needed to get more pilots onboarded started poaching from regional carriers like Cape Air, and let's face it, many pilots would rather fly jets for a legacy carrier than stay with a turboprop plane, unless they are just looking for a quiet local gig that can pay them a nice (but small) regular salary.
Illustrative of how desperate Cape Air is to find pilots is this ad in the BVI Beacon's "Help Wanted" section (https://www.bvibeacon.com/classifieds-april-27-2023/
"Pilot Wanted: Cape Air is recruiting full-time and part-time Captains for its Tortola crew base. Candidates must have the appropriate crew visas and work authorization to operate into United States territories. Minimum hiring requirements are: FAA commercial multi-engine certificate with instrument; FAA ATP (unrestricted); Total time 1,500+ hours; Cross-Country: 500 hours; Night: 100 hours; Instrument: 75 hours; Multi-Engine: 50 hours; FAA First Class Medical. Please email your resume to: PilotJobs@capeair.com."
Finally, putting aside charters, as for commercial airlines with regular service to Taddy Bay from SJU, it's solely Cape Air, which used to have three flights per day, but now only offers two - and that's the case when conducting a search going out as far as November. The other constraint is that among the planes now in service in the Caribbean that can land at Taddy Bay due to its short runway (3,100 feet) are those like Cape Air's Britten-Norman Islander, which although is designed to carry up to 9 passengers, I've never experienced Cape Air loading more than 7 passengers over and above the pilot. Thus, at 14 per day as the maximum passenger load that can come into Taddy Bay, Cape Air can charge "what the traffic will bear," and it's pretty steep.
I priced a November round trip Business Class ticket from Boston to SJU and it was $1,100, whereas per your post, the lowest price on Cape Air between SJU-VIG was $600 - and yes, that's ONE WAY. The length of the runway noted above presents a serious barrier to entry for any other airline, because only a smaller plane can take off and land safely, and with Silver Airlines' ongoing difficulties documented in another thread here, and Air Sunshine now doing only charter service, there's currently no reason for optimism on fare relief in the near term.