I just got the Campmor (Equinox) 8x10 foot silnylon tarp, 14.0 oz. before seam sealing, $80. You only need to seam seal where the ties are sewn to the middle seam. That's probably about as cheap as you're going to get a silnylon tarp. I've been using a 6x8 foot tarp for several years and it's fine as a cooking/dining tarp for 4 (2 adults, 2 kids), but I need the bigger one now that my son's whole family (1 more adult and 1 more kid) will be going on trips.