2015 Prius c tire

I don't think you actually have a choice here, just a confused salesperson. To be fair, lots of fit application guides and databases seem to have incorrect info for the c model

Your car should have size 175/65R15 tires on it. Go read the sidewall to doublecheck. That last 15 in the size means 15".

Using 16" tires would require 16" wheels. This was a factory option available exclusively for the Four trim. If I read it right, yours is the One trim, making it very likely that you need the 15" tires. The salesperson most likely looked it up in a database, saw something that said the car might have 15" or 16" wheels and didn't have enough info to narrow it down further.

Confirm the size molded into the sidewalls of your current tire before ordering anything- but I think you are extremely likely to see the stock 175/65R15 on your car.

...and if you don't mind, maybe ease up on the duplicate posts? I reported them to the moderators so they can clean up after you, but it's really better if nobody has to go through that hassle.

 

If you have 15 inch rims and want to use 16 inch tires you will have to buy four new rims that will cost several hundred dollars.

The 16 inch tires were cheaper because they were possibly not the same type of tire and not from the same manufacturer as the 15 inch tires you were also given a quote on. Additionally, there are supply chain problems for the tire industry and prices on certain tire sizes have risen because they are hard to find. The tire sizes for Prius cars are fairly unique, so that can only make the tires even harder to find and will make them more expensive.

The person who quoted you on both tire sizes without asking what tire size the car currently has was clueless. I would start out by asking for quotes from a few different tire dealers and stay away from the place you first went to. You are allowed to ask questions if you don't fully understand a quote.