During the weekend, I took my kids to see a Katy Perry impersonator at Penrith Panthers Leagues Club. (Don't judge me.) After enduring 2.5 hours of annoyingly catchy bubblegum pop, I came to a surprising conclusion -- not only were the lookalike's lungs indistinguishable from the real thing, her concert was actually better in several key respects. The same can probably be said of most cover bands.
The biggest advantage is obviously price: with very few exceptions a cover band is markedly cheaper than its bona fide namesake. For example, the pseudo Katy Perry concert I attended cost around $15 per ticket. By contrast, the actual singer's last Australian tour commanded prices of up to $250. I'd argue that the "real" concert wasn't 15 times better.
Ironically, the lookalikes usually sound better too. This is because they play in much smaller venues, which results in less audio distortion and fewer technical mishaps. As an added bonus, the smaller venue also guarantees a better view of the performers; even if you're in the very back row.
Another advantage is convenience: there's no mad rush to get tickets and you won't have to line up for hours at the front door or sit through crappy support acts. Instead, you can just plonk your arse down and enjoy the show.
Plus, these people throw themselves into the role with gusto. While "real" singers might have the occasional off night, you'll never see a cover band give a half-arsed performance: after all, their livelihood is entirely dependent on performing live. (Naturally, there's zero chance of them playing new/obscure stuff that nobody likes either.)
If we're being entirely honest, a lot of these pop stars can't actually sing anyway -- so you're watching a "fake" performance either way. At least the impersonator is cheap!
In conclusion, if your kids are bugging you to see a particular band or artist, do an online search to see if there are any tribute versions available. Not only will it cost you far less, your kids will probably have way more fun.