I bought the Betterley one in the UK from the Betterly Importer, it cost £20 plus vat and shipping, total cost was £34 uk ($50) big increase from the US price of $20.
Having said that, it is really well made and I can recommend it. Betterly have included a good method of adjusting the insert so it fits flush with the bed of the saw, I suspect this is not the case with the tape version as it likely sits slightly proud (just my impression though I haven't actually used one).