With the specs that have been said about both platforms, they will both pretty much be in equal footing power wise. The reason why the ps5 will have exclusives is the fact Sony wants to get ps5 consoles into homes asap. I don't think price will be the factor that determines which system will sell better and lets be honest Sony is a beloved company world wide and that is why their consoles have always sold very well even with thier big mistake during the ps3/360 era since Sony made a huge comeback and won the generation console wise.
Sony had a very rough start with the PS3, and it took them a very long time to overtake the 360 in terms of lifetime sales - almost 7 years, by which point the PS4 was about six months around the corner. I don't think they could be said to have "won" the seventh generation at all in terms of anything other than lifetime sales - which go beyond a generation - really. Even then, there isn't much of a gap between the two systems (around 3 million) and the PS3 is actually Sony's poorest performing home console as well. It didn't even come close to the PS2 and it's about 20 million behind the original Playstation. They recovered some ground in later years with price drops and different models, but outright beating the 360? That's a bit of a stretch.
Price was a major point of contention back when the seventh generation started, and if Sony think $600 is going to be any more acceptable now than it was back then, they're kidding themselves. I don't think $500 is going to be acceptable to a lot of consumers either really. I doubt it'll come to that, nor do I think there will be a $100 difference between the two systems, but...well, talking about a system's power rather than its games is a pretty clear (and very flimsy) excuse for an over-inflated price, and you can't use exclusive games to justify it either. I think it'll depend on what the price actually is, but if it's as high as people are expecting it to be, and if there is any noticeable difference between the two at all, then yeah, price will definitely be a factor.
But just because Sony made a comeback with the eighth generation doesn't mean that they can sustain that moving forward, and whilst there is no current indication that they won't, I don't think the Series X is being marketed as a direct competitor to the PS5, at least not initially. That could make a difference in the long run, and maybe we'll see the Series X's lifetime sales overtake the PS5's in much the same way the PS3 eventually overtook the 360's. If, hypothetically, the Series X is cheaper than the PS5 - Sony using exclusive games as a means to justify a higher price for the hardware, rather than Microsoft using system specs and no exclusives to justify a higher price for the Series X - and the price drops further when the exclusives start to roll out, it's going to become a much more appealing platform than it currently is. With Microsoft boasting the best subscription service option out of any of the three in Game Pass, it's only going to be more appealing for that as well.
As a final point, both Sony and Microsoft have their own share of first-party exclusives, but Sony are losing some of their major ones to PC already and I expect that to continue, because PC is a very popular platform and developers want to make money, so it only makes sense. Microsoft have lost some of theirs too, but take out exclusives and there isn't much of a difference between the two systems, and it seems to me like Microsoft are planning for that and playing a long game. Maybe it's too early for a system that has no exclusives right out the door, but I wonder if we'll see a shift in the future. There are other things to consider too - Microsoft's willingness to work with Nintendo and support cross-party play, etc. There are plenty of things that could in the long run make them the more appealing choice. Sure, Sony are more popular now, but they haven't always been this popular.
I realise there is a lot of speculation in this, but you never know how things will go. Sony messed up with the PS3, Microsoft messed up with the Xbox One. Neither of those things means that Sony won't mess up with the PS5 or Microsoft won't mess up the Series X. Painting Sony as the winner before the generation has even started because of this would be jumping the gun, though.