You can use double stick tape to hold sandpaper also. I have a sink cutout from my late brother. I believe he purchased it locally. Works great.
The counter top places like to make money so they will sell you anything they can. I do like the Idea of the smaller blocks.
Until the first of the year MSC ( a company that sells machinist tools) has a pair of solid steel 1 2 3 blocks for under 40 bucks . They do not have the pesky hole in them, great for working with small stuff .http://www.mscdirect.com/product/details/06378186?item=06378186&fromRR=Y