Firstly 35,000 per injector makes it sound like this engine was 2GR-FE D4 engine, which is direct injection in which case the injectors are very heavy duty and very high pressure - extreme long life. Sounds very odd that they conked out. If the cats got choked out it is very safe to assume this fellow was not using the Ilsac GF-5 0w20 oil required for it - they are responsible for it.
Even if it were normal reasonable pricing - e.g. lets say this is a regular off the mill 2GR-FE with ported fuel injection, each injector is about USD 100/- which makes it about 600 for all - this engine does NOT use O2 sensors in the front it uses AFR sensors which have stable readings unlike O2 sensors, if they were bad - a pair of new ones would be in the service order without question, customer doesnt like it - he/she can take his/her car somewhere else.
Lets assume the parts and labor estimate of the repairs are about Rs 100,000/- or even 270,000/- in total (which you said - and Im assuming its a D4 engine) - and the customer is comparing used parts prices with new - then its your job to inform the customer that THESE ARE NEW PARTS.
If a person buys a used Piece of schitt worn out Crown from Japan at half price of new and assumes all repairs should sum up to kabali parts repairs - he/she is a class A idiot. Its bad business.
If such customer walked into my business and said this sort of idiocy to me - I can assure you the only bill I would charge from him/her is the diagnostic fee and let them walk away to their favorite jugaar electrician/cheeta/Dr Denso/chaval/akhrot/mechanic who would throw used parts in it and then pray it works - and if it does not work then say - Bhai ye fail gaadi hai.
I have better things to do with my time - and I can guarantee it will come back - and I would charge even more to remove the "jugaarbaazi of favorite person"
Trying to mask a problem is not solving it and is considered bad practice. e.g. If my firm get a contract of starting up a fresh enterprise and have to set the Global Catalog, Domain, Forest, Directory, GPO, Email, and other DBs too - and all I do is create everything on the root without any containers or security groups - its considered bad practice.
It will work but cannot be audited. Just like if you fit a device that masks problems - then its only till the next person to uncover it and prove it wrong - a car is built to a set specific service standard and subsequent service manuals are written for it - just because its standardized. How do you expect someone to repair an item which is not standard.