I agree, if that price is for just the spray and you have the existing slab, that is waaaaaaaaay high. SunDek should be between $3-$4 per sq. ft., tops. Now, I am NOT a pool professional and I do not know if you have to scrape the old deck to prep but what I do know is that you could EASILY apply this yourself (assuming you can cover what is there). The stuff is designed to spray on or roll on. Also, Sherwin Williams makes an acrylic coating (same as Sundek) that you could easily go and buy. I think they are even having a 35-40% sale right now. It is called UltraCrete. You can roll it on, like Sundek. We just had (and almost done) a pool built and I have 1150 sq ft of deck. 1050 was spec'd, ended up with 1150 and I was charged $10/sq ft. for the extra 100 sq ft, which was the concrete and the Sundek. I thought that was high but my PB did have a concrete sub who was proud of their work by $3-$4/square foot compared to normal Houston area pricing… Nonetheless, they did excellent work and the screen enclosure guy said he never ran across a slab "this straight".