Is a cheaper bidet worth it?
For a first bidet, yes. Most people who are unsure whether they want one are better served trying an inexpensive model than committing to a premium seat.
The main thing to check is whether there is a power outlet within three feet of your toilet. Without one, you are limited to non-electric models regardless of budget.
What you get under $500
At this level you are choosing between a simple non-electric attachment and an entry-level electric seat.
Non-electric models use cold water and mains pressure, need no outlet, and fit in about twenty minutes. Entry-level electric seats add a heated seat and warm water, but heat it in a small tank — so the warm water lasts around 40 seconds before it needs to reheat.
What you give up
Instant unlimited warm water, warm air drying and auto open-close lids generally start above this range.