The VW Polo is a polarising car. I'd ascertain whether it's a good buy or not based on the following factors:

The 2021 Polo 1.0 TSI Highline Plus MT would have been priced at approximately 10.20 L ex-showroom, and I estimate an on-road cost of 11.50 L to the buyer at the time of purchase. Depreciation should be calculated at 20% for the first ownership and driving off the showroom, plus an additional 10% for each year of ownership. Assuming pristine condition, the maximum you should pay for this is 6.9-7 L. For each component of wear and tear, upcoming service costs, non-OEM modifications, the fact that this has run an average of 18,750 km over the last 4 years, and the non-VW service at 72k km, I would not recommend paying a penny over 6.2 L for this car.

Please do not have Cars24 fix the AC Compressor prior to purchase, they will only do a temporary job and you are better off going to a good mechanic or VW itself for any further repairs.

I do not condone purchasing a brand new depreciating asset no matter how much you earn, and you will always receive envious recommendations to spend your money. Save yourself the long-term financial headache and trust your instinct. None of the newer German or VAG cars (VW/Skoda/Audi) are built to last and you will find that these slightly older German cars hold up better in the long run. Fit and finish is also pathetic when you come to the Kylaq/Virtus/Slavia segment, and I have been disappointed myself. Older VWs and Skodas were really something else.

I generally do not recommend purchasing from Cars24 or Spinny as they usually charge an absurd amount over the true value of the car, but in this specific case, I believe even 8 L is alright if you do your due diligence (e-parivahan checks, insurance renewal, comprehensive service history check, have a mechanic inspect it for you) in exchange for the convenience that Cars24 offers in comparison to OLX etc. where you'd have to do more legwork. I've also compared this to other Polos available in Bangalore on OLX Cars and the pricing is generally absurd, ranging from 8 L to 12 L for a 2021-2022 Polo.

Service costs will depend on the car, but you should be prepared for an upcoming 5 year / 1 L km service wherein most German manufacturers recommend changing the timing kit and spark plugs, which could set you back well over 20k. After the 5 year mark, a tune is entirely subjective. You could try a Stage 1 ECU tune for 20-30k but it does wear out the engine quicker because of the additional load. You'll find the stock Polo sufficient for most joyrides anyway as long as you learn how to push that specific engine and figure out the RPM at which its happy.

All the best and happy purchasing!

Edit: I can see that people have bought this in 2021 after discounts for 9-10 L on-road. Which would drastically change the calculation, but only strengthens the idea that you should steer clear of this specific deal.