在真机上调试是不是必须买开发者账号？

是这样滴，花银子吧。

听说Xcode 7可以不用加入开发者计划也可以进行真机测试了。

不放上AppleStire不需要开发者账号,除非你要用到iCloud等

4. Enroll in the Apple Developer Program (Optional)

A common question about developing an iOS app is
whether you need to enroll in the Apple Developer Program (https://developer.apple.com/programs/).
The short answer is optional. First, Xcode already includes a built-in iPhone
and iPad simulator. You can develop and test out your app on your Mac, without
enrolling in the program.

Starting from Xcode 7, Apple has changed its policy
regarding permissions required to build and run apps on devices. Before that,
the company required you to pay $99 per year in order to deploy and run your
apps on a physical iPhone or iPad. Now, program membership is no longer required.
Everyone can test their apps on a real device without enrolling into the Apple Developer Program.

Having that said, if you want to try out some advanced
features such as in-app purchase and CloudKit, you still need to apply for the
program membership. Most importantly, you're not able to submit your app to App
Store without paying $99 annually.

不需要啊，发布才需要