Minimum and tiered pricing

Hello there,

I’ve been searching for a while now for a suitable solution for my shop where I want to sell voiceovers by the word.
I know it’s pretty easy to set up some variable discounts, but I want to charge the same amount (￡10) for any voiceover that is 200 words or less for the same price (effectively I have a minimum purchase price of ￡10).

For 201 – 1600 words I want to charge ￡0.05 per word – so 750 words would be ￡10 + ((750-200)0.05) = ￡10 + ￡27.50 = ￡37.50

For 1601 – 4000 words I want to charge ￡0.3333 per word – so 1750 words would be (￡10 + ((1600-200)*0.05)) + ((1750-1600)*0.03333) = ￡80.00 + ￡5.00 = ￡85.00

For 4001 > I want to to charge ￡0.025 per word – so 4500 words would be (￡10 + ((1600-200)*0.05)) + ((4000-1600)*0.03333) + ((4500-4000)*0.025) = ￡80 + ￡80 + ￡12.50 = ￡172.50

Or you could consider it like this; I will charge ￡0.05 per word for the first 1600 words, but subject to a minimum of ￡10 (is this something that is possible?)
Then ￡0.03333 per word for 1601-3900 words
Then ￡0.025 per word for 3901+ words

Any advice would be gratefully appreciated.

Cheers,
Alasdair