I don't think the PSLV actually falls in their market. It has a payload almost 10x what the Firefly alpha would offer, and it has a $15 million price tag. Frankly, if the Firefly alpha is offered at anything other than single digit millions of dollars per launch it will not be commercially viable. I think the company is aware of that and that has driven the design of the rocket. The Firefly alpha is an enormously simple rocket, and is theoretically designed for ease of manufacture. It also uses incredibly inexpensive fuels which are easy to store.
ISRO was/is developing a smaller variant of PSLV called PSLV-3S. It is a three stage variant of the regular four stage PSLV (they removed 2nd stage, and strap-on boosters). PSLV-3S payload capacity is 550KG to LEO. However, I don't know about latest developments on it.
If Firefly can get their weight down by use of better materials and a more efficient engine then they could get a significantly lower cost to orbit. That's a big if, but I say it's worth the attempt.
Their own press release [1] says that "this efficient, brand new vehicle is capable of carrying 400kg into low earth orbit [...] for [...] around $8 or 9 million".
Wikipedia [2] says that the PSLV can lift 3250 kg into low earth orbit, for $15 million.
The Firefly Alpha costs 20,000 USD/kg. The PSLV costs 4615 USD/kg. It's four times more expensive. How much would they have to bring the weight down to be as cheap as the PSLV?
