There is a little difference between these two words. 付费means pay a fee, 支付is the action of paying. But they are both used more often in written than oral. We usually just say 付钱. Hope this can help you.

Yes, there are. 付费 is a verb that can only be used passively, meaning something is not free or needs to be paid. For example, "这个电视频道是要付费的". 支付 can be used as a verb or a noun, meaning "pay" or "payment method".

I think 付费 is often related to a sevice and is more like the word 'cost' in English while 支付 is more like the word 'spend'. And when you use 付费，you may say 有线电视需要付费吗？As it is shown in the example, there's no object behind the word 付费，so it's more like a vi. And when we use支付，we may say 我们需要支付多少钱？There IS an object behind the word 支付.Besides, 支付多少钱seems like a phrase in Chinese. SO I don't think these two words could be used interchangeably at all times, in fact, I don't think they could be used interchangeabley at all.

补充点 付费 and 支付 他们都有动词 和名词的意思，所以注意词性，有利于你的理解~

付费=pay the money 费 in this word means the money. 支付=pay