You get unlimited personal challenges with a subscription. I am the admin of a bike-focused online community and I regularly make challenges for members of the group, often a group challenge but also individual challenges. I know that our banter about a certain challenge, over the 5 challenge limit that a member had reached, prompted that member to subscribe. People place value on different things, and there I guess it was frustration at missing out, having been involved in all of the previous challenges, that prompted that person to subscribe. There can be hidden value in it, is what I guess I'm trying to say, or value to people that is not immediately apparent.