if statement Simplification

The Ebay fees: (This is not a working formula, its simply showing what I want the formula to say.)
('Inventory!'X * 'eBay Fees'!H) + if > 50, add ('Inventory!'X * 'eBay Fees'!I) + if > 1000, add ('Inventory!'X * 'eBay Fees'!J) + 'eBay Fees'!G
The row numbers are dependant on category shown ('Inventory'!D)
This column is to show the Ebay fee which is then added to columns J through P.

The Paypal Fee:
('Inventory'!X + 'Inventory'!Y) * 'eBay Fees'!H (2.9%) (2.5% if sum of 'Inventory'!X:Y > $3000)

I dont know how to make it any simpler than that. Look at the formulas that are in the spreadsheet already to show where everything is suppose to point.Im including the two worksheets again. inv97-03.xls is the current one. ebay1.xls is my old one that works but you cant choose category (Column D) or or price variable