There are two main components to cycling shorts (or bibs), the lycra & the chamois. More expensive shorts have better lycra; the more it compresses the muscles the less your muscles will fatigue allowing you to ride further/faster/longer.
The chamois is the padding that you sit on. Years ago it was made from genuine sheepskin. Now they’re almost all synthetic. You want your chamois to provide padding & moisture wicking; the best ones are ergonomically designed to have no/few seams/no seams in certain areas to prevent chafing. I’ve seen cheap ones made of open cell foam; not breathable & excessive compression when sitting on them; in short they look like better ones but they suck.
You didn’t put a link to what your considering & I didn’t try finding them either so I have no specifics about the ones you’re thinking about, but in general I wouldn’t expect the t-shirts you’d get at a discount store that sells them 6 for $10 to be the same quality as more expensive ones you get elsewhere. Same rule applies here. Usually, $30 cycling shorts are crap & I wouldn’t personally buy them.
wguy123 specifically mentions Pearl Izumi. If you look at shorts (or bibs) on their website you’ll see that even within one manufacturer the best ones are more than twice the price of the cheapest ones. They all kind of look the same but it’s different materials that make the more expensive ones more expensive.
Now, you’re talking an upright bike, which has you sitting on different parts of the bone than a traditional road bike. You also says it has a wide seat; these are typically more padded than a road bike seat. Finally, you state this is for an indoor bike; people tend to ride indoors for shorter periods of time then they do outdoors; therefore some of the things, like muscle fatigue, don’t come into play. When you consider all of these things, cheap cycling shorts don’t really matter as much.