"He said 7 slabs had to be raised/leveled in order to fix that area. He wants $280 ..... "

What method?

Mud jacking?

Lift and pack?

Mud jacking

That sounds like a reasonable price then for just about anywhere.

Seven slabs is only $40 each.

It takes more the one person and equipment.

brickeyee, I agree its a reasonable price for all 7 slabs. but I dont want to do all seven, I just want to fix that little area where it has sunken.

Can i buy some concrete and try to level it myself from the top? like put a layer over the sunken area till its level with the other slab?

Another alternative, and you might feel that it would be a less esthetically appealing one, would be to rent a grinder (you'll have to buy the blade) and grind it down, tapering back about 5".

I thought about grinding it down, will the color of the newly ground concrete eventually return to the natural color of the rest of the slabs?

"I agree its a reasonable price for all 7 slabs. but I dont want to do all seven, I just want to fix that little area where it has sunken."

It is very unlikely that the concrete is actually seven separate pieces (slabs).

Unless you plan on cutting the sidewalk into separate pieces you have to everything (the whole piece_ at the same time.

I would bet he is using "slabs" loosely to mean lengths of the sidewalk between tooled in fracture lines.

"Can i buy some concrete and try to level it myself from the top? like put a layer over the sunken area till its level with the other slab?"

You can try, but it is not going to bond well, and you will be just as alarmed at the price of the epoxy concrete you would need to pull this off.

Concrete tapered out does not have along life, and if you get freezing weather may not even last a single winter.