Alright, it's not a secret, Prague is getting loaded with tourists. I would be tempted to say "don't go there", but it's a beautiful and unique city. It's worth a visit. So here's what I'll say instead: "go there at least once, but be smart and respectful".
The thing is, accommodation prices in Prague have gotten crazy.
So here's how to find a cheap place in Prague:
A 30-minutes ticket metro only costs 24 CZK in Prague! That's around €0.90! And look at the map, all metro lines (there are only 3) go to the city center:
30 minutes are enough to go from any station to the city center. The round trip will cost you less than €2 and you'll be able to save a ton of money on accommodation, whether you're in a hotel or an airbnb.
You'll notice that a lot of tourists have more respect for their Instagram account than they have for this awesome city, don't be like them.