Well, that is the whole point why solutions like Photon exist: it’s quite a lot of work to develop a proper backend solution from scratch and it’s normally a lot cheaper to make use of existing 3rd party solutions than to pay developers for reinventing the wheel and for implementing all the low level basics themselves.
With Photon Cloud another advantage is, that you also do not have to host the Photon backend on your own servers and therefor don’t have to pay someone for server maintenance on your self hosted servers.
Also, don’t forget traffic costs. They are a huge factor and actually the main cost driver for realtime multiplayer. For example 1.000 concurrent users generate about 10 tera(!)byte of traffic per month for the average game on Photon Cloud. Feel free to compare different cloud hosters like for example Amazon or Azure and see what this amount of traffic would cost you there.
So, yeah, I would say, that Photon is quite a good option.
However as I am one of the Photon developers myself, I am of course a little bit biased.