Urgent nesting calculation issues

Hey all!

I've got an issue I'm trying to wrap my head around. At the moment we manually do all of these calculations, but if we could create a formula to do this it would definitely streamline our process!

At my work we have a spreadsheet we use to calculate estimated current prices of our supplies. This is based mostly off of quantity, and years since last order.

The way it works is we have a Historical (last used) price and quantity. from there we adjust it to reflect a more accurate current price.

In general, every year our supplies get 3% more expensive, so the further back our last order was, the more we'd have to compound that 3%. We round our years, so if the last order was placed on 6/7/16 then as of 5/2/18 it's still only counted as 1 year.

Furthermore quantity ordered plays a huge part, for every time we order double from the last order, we get a 7% Discount. So if our last order was 10, and now we're buying 80, that would be a discount of 21%.
Conversely, every time we order half our last order, we are charged an extra 7%

What I have to work off of is: Historical Price, Historical Quantity, and Targeted Order Quantity. Trying to estimate the appropriate Current Price taking into account the 3% annual increase, and 7% increase or decrease depending on order quantity.

Any help is greatly appreciated,

Thanks in advance!!!!