I do tell people I meet at stores that it's fifty bucks for the first fish unless they're just taking it home to kill it.
Gets their attention right off and they ask me why, so I point behind me at whatever supply I was looking at.
Mesh Top $10.00
Tetra Filter $10.00
Water Treatment $3.00
You can skimp on a lid, or the heater, etc. But for your fish to have a fighting chance you need to buy about fiddy bucks of stuff if you don't know what you're doing. This is where they make their money.
I tell the store employees that, quite simply, a person who enjoys the fish and can keep them successfully will not only come back for food, ornaments, replacement filter media, chemicals and medicines, but they'll come back for fish AND send their friends if you're kind enough to explain the actual basics and they're still interested. This is why Aqueon puts heaters in it's 10g starter kits and charges a fair price hood included. A betta is a fish and you can either waste the $15.00 for the cute little awesome OH he died bowl or you can consider it an investment in a pet and learning a hobby.
An aquarium is probably the single most durable hobby supply I've ever owned, short of my 1983 Blue Chip XT's motherboard. (wow, tough thing)