This really is an arbitrage. It is caused by differences in supply and demand between the interest cashflow and the principal cashflow and by differences in the financing rates on the two STRIPS.
As you noted, the price difference is small, and it would take 30 years to guarantee convergence. In addition, the outstanding amount of the 30-year coupon strip (the interest payment) is quite small, since the only source of this cashflow is the 30yr bond itself and therefore the amount available is only half of the annual interest amount of the bond - if you're talking about the current 30yr, only \$250mm can be stripped compared to a \$16 billion principal amount. Therefore, it is currently not particularly attractive as arbs go.
Finally, if you were going to try to capture this arbitrage by shorting the principal strip and buying the coupon strip, you would need to borrow the principal strip and finance the coupon strip. A price difference of 1% is approximately equal to a yield differential on these two instruments of 3 basis points. As a result, if the interest you earned on your short proceeds was just 3bp less than the interest you paid to finance the purchase over the life of the trade, you would not make any money on the trade.
Generally speaking, the principal strips or "P"s usually trade rich to the coupon strips, but this is not a hard and fast rule. At times this arbitrage can become quite large, as much as a 3-5% price difference between two bonds.