*This is a complete 4x4 table of LoS-blocking terrain for $16 (2x $7 foam cans, $2 craft paint.)
*It took only an hour to make. (excluding foam drying time)
*It has a coherent theme.
It is very cheap.
You get plenty of foam from a can. I actually have 4 more leftover terrain pieces I'm using for another project. (It will be a lava hell-world)
Beyond the bare minimum....
*The trees were $10 for 30 from eBay and sit on 50c MDF coasters. However it adds to the cost.
*Obviously you could add in foamcore buildings, but the investment in time climbs sharply.
*Drybrushing the paint on the "cliffs", and adding small scattered gravel-sized rocks would improve it a lot.
*If you want to make the board mobile, you can glue the sand to the baseboard by painting it with 50/50 PVA/water mix.
*You could easily adapt it using white sand and grey paint for a "snow" environment.
*The whole sand table cost me $22 and 15 minutes to make.
As you can see, plenty of line-of-sight blocking terrain makes this a solid Infinity table. It would work equally well for Heavy Gear, Tomorrow's War/Force on Force or any game that requires lots of cover.
I'd welcome ideas for other cheap, easy-to-make tables. Put a link in comments?