How much topsoil do i requirement and how much would it cost me? Well, recently i have a severe grub infestation that nearly killed...

Well, recently i have a severe grub infestation that nearly killed my entire front grass. So i got roughly 400-500 sq ft of all out open to the elements spot and the soil is becoming sandy due to the rain and need of nutrients ( the lawn have since been treated twice next to grub ex) So i'm planning on using a garden tiller to turn the soil, and then to lay down fresh top soil over that. After that put down seed and fertilizer and cover it with hay, and unsurprisingly water, hose and water.
So:
Lawn Coverage: 500 sqft at 2-3 inches

How much top soil do i involve, and if you have any tips or corrections that i should craft to the steps, let me know.

I know they charge nearly $25 a cubic yard, hope that help.
Answers:    To cover 500 square feet beside 2 inches of topsoil you will need 3.08 cubic yard and to cover it 3 inches deep it will clutch 4.62 cy. I think I would till the patio first and see what the resultant soil looks like. Usually it is just the top inch or so that leaches out from rain right away. You may be capable of just till within a bit of compost, peat moss etc. without the expense of top soil.
1 cubic patio will cover 162 sq ft at 2 inches
1 cubic yard will cover 108 sq ft at 3 inches