My battery drains faster than usual. It says it’s degrading. How much does it cost to replace the battery or should I switch to an Android?

I'm not sure what you'd gain by switching to an Android. The batteries in Android phones degrade just like all other rechargeable batteries.

I think I disagree with KiltedTim a bit here. Whether you decide to replace the battery versus being a new phone depends on your needs. It will probably be another year, possible more, before you start running into problems being able to download apps. While a new battery won't make your iPhone 7 do what current models do, it will certainly make it feel almost like new again. If your needs are simple, replacing the battery is a cheap way of getting more life out of your phone. It will certainly buy you time to think about what you want to do. Also, if you decide to buy one of the new releases in the Fall, there may be a wait. Having a reliable phone to use may make the wait more bearable.

However, if you decide that you want to buy "last year's model" (still great phones) right now, then no, don't bother replacing the battery. Put the money toward the new phone.

iPhones have a track record of being supported for OS updates far longer than any Android based phones.

The iPhone 7 came out in 2016. It continued to be sold until 2019. It has continued to receive ios updates all the way from ios 10 through ios 15.

I wouldn’t invest the money in replacing the battery in a phone that old. It’s time for a new one.