I assume you think Thea de worth it since you keep buying them. Domyiu get the platinum or gold or silver? I am particularly interested in the Spelljammer one.
I have the Platinum Spelljammer and Dragon Heist, the Silver Saltmarsh (which I think is the only one they made) and the Legendary Strahd (ditto).
The composition of each is slightly different. My priorities are battle maps, minis, and hand-outs, in that order.
The Strahd set is worth the price of admission for getting full-color battlemaps for the entirety of Castle Ravenloft. It also has great handouts, and cute puppets which I will never use. No minis.
Dragon Heist has color battlemaps for many areas, which is particularly good because the maps in that adventure are the monochrome Dyson Logos ones that I don't really like. It also divides the adventure into books for each season, which eliminates the page-flipping nightmare of using the hardcover. It has nice handouts including a great Stone of Golorr. It includes a generous selection of (unpainted) minis. Unfortunately this is among my least favorite 5E adventures, but that's not B&G's fault.
Saltmarsh one has no minis and frankly also sadly missing battlemaps for most of the adventures. Handouts are very good.
Spelljammer is probably the strongest of the four I own. AMAZING collection of painted minis, many of which are otherwise unavailable. Color battlemaps for most of the important encounters. Only a few handout props, but the ones included are excellent (love the ring of shooting stars). The only thing I wish they had included is a Spelljammer ship model al la the infernal war machine included in the Baldur's Gate: Descent into Avernus set (my group got that one for a DM who had run Tomb of Annihilation for us).
The way I have acquired most of mine is by my players pooling their funds at the end of a campaign to get me one as both a present and an unsubtle hint that they want me to run it. I think that's the way they make the most sense to buy, because as a group gift they're much more affordable and then everyone gets enjoyment from them although the DM owns them.