I love artisan soaps, and I love the bargains I can get on Amazon. But IME artisan soaps on Amazon are always at least full price and usually more than that. Bargains are few and far between.
There's nothing wrong with buying a great artisan product on Amazon and maybe paying a small premium. But the best bang for your buck is going to come from top-quality commercial products.
Prices fluctuate from day to day, but if I were to buy something right now it would probably be a puck of DR Harris Windsor in a mahogany bowl and a bottle of Fine Accoutrements L'Orange Noir.
Kick in another $2 of your own and you have enough to buy a puck of Pre de Provence. You'll be hard pressed to complain about anything in that lineup.
highly recommend pre de provence soap (for example): https://www.amazon.com/Pre-de-Provence-Shave-Soap/dp/B0026DWB7Y?th=1
It's under $10, and you can use it for months before even making a dent in the puck...
I've heard bad things about the Body Shop synthetic. Specifically, when the Plisson first came out, a lot of people were afraid that it would use the same knot as the BS brush, and were relieved that it didn't. Then again, that was a year or two ago, so maybe things have changed. It'd be interesting to hear from somebody with first-hand knowledge.
While I love my artisan soaps, on Amazon I tend to gravitate toward the bigger producers. Pre de Provence is amazing stuff, and right now it's $11 shipped for 150g - that's got to be one of the best values on the planet. You can also sometimes find great deals on Cella, DR Harris, Tabac, and Valobra, although none jump out at me right now.
Try a Blade is definitely a better option for shave samplers.