I drink a lot of wine and was really excited to see this thread. Maybe, like numerous gun and whiskey threads before it, we'll have a longer-term, ongoing back and forth about wines we try and like. I'll echo what a lot of posters have said so far: the relationship between price and quality is not linear (above a certain threshold, anyway), and "quality" is not at all the same as "do I like it?"
There is definitely a class of wine that is made in bulk, not aged in barrels, and adulterated with chemicals to give it specific colors, aromas, and flavors. These are generally in the <$10 range and should be avoided. Whether they "taste good" or not, these are of poor quality and don't reflect what I think is the true joy of wine: an agricultural product that is nurtured and created, a blend of sun, time, and whatever you're feeling at the time you drink it.
Getting past that class of wine, there is a whole world of styles, prices, and tastes, and a general rule is if you like it, it's good. Some regions, like bordeaux, have rating systems that have been in place so long they probably mean very little, but the higher ratings definitely mean higher prices. There are MANY bordeaux makers that either were not around in 1855 when the classification system was created (and not since changed!), or just haven't gotten on the radar of critics, that are excellent. I drank a $16 bordeaux last night that was really beautiful, and I buy from a "fifth-growth" (the lowest of the left bank grand cru ranks) for $189 that are easily as good as the "first-growths" at 1/10 the price.
It is also true that Napa cabs, over time, have become a little more like bordeaux (austere, mineral, savory), while bordeaux wines have become a little more like Napa (bigger, fruitier). Someone mentioned Cote du Rhone, and I couldn't agree more. For the price, southern rhone is a hotbed of big, bold, flavorful wines, but I disagree that you can't find them. On wine.com, right now, I see several bottles under $30 that I know to be good based on my own experience, or having had other things from those makers. Guigal doesn't make a bad wine, the family Perrin is reliably great, vieux telegraph... Rhone is also the region most like how the US regions are defined: Napa as a region, with specific appellations within it (e.g., Oakville, rutherford, coombsville, etc) , so it's a little easier than, say, with burgundy or bordeaux, to know what you're really getting (e.g., you can buy cote du rhone, sourced from a large area, or appellation-specific wines like Gigondas, Chateauneuf du pape, etc, which will cost more).
Rioja is also a tremendous value proposition for big, bold flavorful wines. I'd add that the spanish tradition is to bottle-age their wines longer before releasing, so whereas you're seeing 2018s from CA right now, Rioja is mostly releasing 2012s now. The result is you get aged wine at a better price because, for whatever reason, the market has decided that it doesn't want to pay french prices for spanish wine. Racist, perhaps, but... Rioja also has a simple rating system. "rioja" is the least-barrel-aged, crianza next, then reserva, then gran reserva.
CA, generally speaking, is really expensive. Some of it is outstanding, but I definitely think it's easier to find great wine at low prices in the regions I mentioned above compared to CA.
Anyway, looking forward to seeing what else pops up on this thread!