@MCB18 thanks for chiming in! Others, too, of course, but I was particularly looking forward to your response since I knew you are deeply involved in this.
As with many of these things, much depends on whether/how much one values their own time. Of course, when speaking of a hobby, it's difficult to determine an hourly rate. Still, if we do so for amusement's sake and put a very modest $25/hr to your labor, we arrive at $100-$250 in labor. Across 30 rolls, let's say $3.25 to $8.25. Add to this the base price of $5 for the film itself, bringing the total up to $8.25 to $13.25. As I understand, Arista 120 film retails for ca. $6.50 (e.g. B&H).
Now, of course I understand that there are other motives involved. From the financial perspective, the hourly rate I mentioned is of course fictive/hypothetical and it doesn't represent an out-of-pocket cost. If you're in a position where you want to save every penny, evidently, the value of your time drops in relation to the pennies saved. Also, what
@MCB18 does is making available (to himself as well as others) types of film otherwise not accessible to photographers; for someone rolling for themselves, this can of course be a motive. And I can imagine someone enjoys the DIY spirit and having been manually involved in as much of the process as possible (consider wet plate on a DIY camera!)
I guess this brings me to the question:
Why exactly would it be nice? Decide accordingly. It may seem nice, but if the economic perspective prevails, I expect you're better off buying the commercial product, provided you approach the matter rationally.