I maintain/feed my starter with the following formula (by weight):
1:2:2 (starter:water:(rye )flour)
I keep it at room temperature until it doubles (3 to 4 hours) an then put it back into the fridge. I wouldn't use less new flour; but with this formula I never in years had a sign of under-feeding. During 1 week after the feeding I use it directly from the fridge as seed for levain or now for starter in pizza.
So every time I feed my starter, it quintuples.
The minimum of starter I think is feasible to have is 10g. Therefore, every time I feed my starter I put back at least 50g. As I want to feed my starter at least once a week, I have to at least use or discard 40g during one week.
I know, If you just produce pizza, 40g of starter will leaven 4kg of flour (more than 20 pizzas) which usually is a lot for home bakers. If you produce leaven for breads, 40g is very little. It will produce 1600g of leaven (5% starter; 100% hydration) and will leaven about 2,4kg of flour for strong sourdough flavour (same amount of flour added to final dough as leaven) or again 4kg of flour (twice as much flour as leaven + flour of the leaven itself). Often even 10% starter is used so it will be 1,2 to 2 kg...
And even if you have to discard 20g of the starter each week. Here I pay 86 cents for 1kg of flour. This would be less than a cent for the discard; about 45cent in a whole year.
If you bake "a couple of times a week", those 40g may even be not enough.