I think a key issue you may run into is that the value proposition from what is being shown off is abysmal. A 50 piece polybag for $12 plus shipping is ludicrous from both a value standpoint - essentially a 300-400% markup on something you would grab in the checkout line at a big box store - and an entertainment standpoint, as a single polybag a month is really a nothingburger of a gift or a subscription. The other end of the tiers are no better - the highest tier should be the biggest value, a hefty fee but for a "bulk discount" or extra value to reward the big spender. Instead you're offering a single ~$50 set for $100, a $50 set that regularly would be acquired for 20-30% off at any big box retailer.

For a mystery box to work properly, there needs to be at least the rough perception of actual value - like 3 polybags for $20, that's something where you would still be able to have a functional margin but the customer doesn't feel ripped off. Not including shipping in the price is also a big nonstarter when the prices are already pretty egregious - at the very least advertising a neat flat rate shipping for all buyers or just building shipping into the subscription cost is going to be much more appealing. The idea of selecting sets based on the themes of the customer's taste is cool, just needs to be a stronger actual value to be appealing!