How To Motivate A Neural Network
I think your input features are lacking. Firstly, The budget allocation is not simply done based on the previous year turnover and size of the company, there are myriad other factors involved which directly correlate towards a budget allocated to any department.
Secondly where is the relation of profit vs budget allocation? For maximizing profit according to budget allocation, your training set needs to reflect that.
Thirdly you could simply make target profit an input feature and model your data accordingly to allocate budget keeping in mind the targeted profit as well. Provided you incorporate features highlighted in the first point.