You would be surprised what a russian can climb. Mine used a plastic chair leg and a cinder block one time to shimey up between, took her two mins. Thank goodness I was out there at the time and she didn't get out lol. I aslo watched her climb a fence, no kidding
Think those pavers can fall over? Even if 1 is nudged creating a gap....could be an escape route!
What size enclosure were you able to make it with the $50 worth of pavers? If I remember correctly... The 2x10s that are 10ft long are about $15 each. Buy 4 of them and for $60 you have a large 100sqft pen (10x10) that can be screwed together and maybe be more stable than the individually standing pavers? ..Just a thought.