Shipping rates:

I have 2 flat shipping rates based on the location my products are being shipped.

I have a problem where if a customer orders multiple of any item, the flat rate stays the same, it does not multiply. I need it to multiply because the flat rate is per box.

My website developer is telling I have to pay for a plug-in to get my website to charge the shipping rate per item. So for instance, customer buys 3x of one item they pay 3x the flat rate.

Is this actually a limitation? It seems so minimal, if someone buy 100x of an item how would I ship it for a single flat rate of $5?