In your settings add an additional formula for the AMAZON.COM or AMAZON.CO.UK
abs(((((vendor_price-48.995)+abs((vendor_price-48.995)))/2)/(vendor_price-48.995)-1))*6
This formula ll place an additional charge of 6 if the price is less than 35
You can edit and replace the 6 with what ever you want to add for shipping cost
For UK users .you need to edit the formula and change the formula with the UK settings
abs(((((vendor_price-19.995)+abs((vendor_price-19.995)))/2)/(vendor_price-19.995)-1))*6
replace the 6 with the shipping cost you want
If you try to use it on other suppliers DO NOT put in formula the exact amount of free shipping