questions from a flat rate VAT self employed guy

hi, First time posting here

I’m a self employed sole trader, my question is in regards to how much I’m charging my customers and what the costs are to myself (I’m flat rate registered)

for example if i purchase some equipment from my suppliers at £200 + VAT I’m paying them in total £240
I then charge my customer £333.33 + VAT with my customer paying £400 total for the same product with my own programing

my question is basically as I’ve already paid the VAT on my original purchase surely the vat element when i resell the item should only be on the extra that i charge on top as I’ve already paid the vat when i purchased the product

I’m struggling to get across what I’m trying to say here

hopefully someone gets what I’m aiming at, basically if I’ve already paid the vat on the original purchase, why then should the government get the vat again on the same product when i resell it? its making what I’m selling way more expensive than all the other re sellers who must all buy it from the same provider as me (as their the only manufacturer) (and I also know my competition are definitely paying the same as me from the supplier)

hopefully someone reads this and can offer me some sort of advice!