The question is:

What is the total cost of the trip including money others will be giving you?

Do i need to calculate the total price of the trip regardless of who is paying?

Next:

Do you have savings or income from other sources?

Yes, we have savings, but it wants to know how much monthly income we get from them? So how can i answer?

Cost of trip; yes, put the total (estimated) cost, regardless of who is paying. If you or a third party are paying for all or part of this, explain this in your sponsor's letter.

Income from savings and/or other sources: simply say how much the income is, if zero say so.

Thanks.