Gantt Chart as a Standard Feature
Gantt charts are used in a wide variety of cases and are very popular. It seems Caspio is taking advantage of this, leaving less used and desirable Chart Types as Standard options, and adding the Gantt chart to the premium 'App Extensions' list.
The minimum you need to pay for a Gantt Chart is $750, which I imagine is for the complete bare-bones version. We already pay enough every month for your services, I believe a Gantt Chart in the Standard selection of chart types is more than manageable.
Even if you were to leave the bare-bones stuff as standard, and advertise better features as an App Extension. But, taking highly requested features from the Ideabox and putting them behind a paywall is really not cool.