Option 1: Original Leather - Best in fit / finish, summer / winter comfort.
If you have the budget, go for it. Leather seats will easily outlast life of your car and if maintained well & will remain cleaner too. For Ertiga it might cost 40K.
Option 2: Fabric - Cheap, Better comfort in summer, Washable options
I am never a big fan of fabric seat covers since they tend to become very fast and difficult to clean as well. But some stain resistant materials are available I understand and if done by experts, the fit and finish could be good also. But there is also risk of these covers gathering wrinkles after use for 2 - 3 years
Option 3: Faux leather / Leatherite .. - VFM
option, Easy to maintain
There are many ready-made options with this material. Autoform / Autofoam brand seems to popular and I have prices of these seat covers in ebay around 8K. I had seen similar price at Reliance Mart too. Delhi is the best place to get them really cheap and fixing can be done by any accessory shop guys.
Local accessory guys can also getting this done in made to order mode. When I checked I got quotes from anywhere between 8K to 15K for similar looking material. The best part is - you get to choose different stitching and color combinations to your liking. Bangalore could be best place to get custom seats made.
There are 2 material types - one thinner material referred to rexin and another thicker material with foam layer on the back. The later is supposed to be more durable than the later & because of extra layer it offers more cushioning as well. Only down side is these covers get heated up in summer - but that problem is there with some types of fabric seats too. Best to avoid dark colors.
Good luck with the hunt..
I had narrowed down on getting custom stitched seat covers with an accessory guy. But accidentally came across 'DORADO' seat covers in an accessory shop for around 7K. Since the color exactly matched the dashboard and fit / finish was very good bought it without much thoughts. Sharing some photographs of my seats..