What is the approximate cost of resurfacing a cement slab?

Nationally, the average cost for concrete resurfacing is $3 – $10 per square foot, depending on the condition of the original concrete and local labor costs. For smaller projects, some contractors charge a flat fee of at least $500 – $1,000. The new concrete must also be sealed, which costs $20 – $80 per gallon.

I think it'll depend on how you want to accomplish the task -- if you're looking to pour over existing concrete, you'll need to get a quote from a concrete provider. Or check prices of bags and a mixer rental at your local hardware store.

See if this helps:

https://home.costhelper.com/concrete-resurfacing.html

Not an easy task.