I don't agree that the scope should cost as much as the rifle. That's only important for people who want bragging rights on an internet forum IMO.
And we all know what opinions are worth...
How much you pay for an optic depends on a lot of things, including your budget, the rifle's intended use, and what you want.
If you
want to put an ACOG on your 15-22, can
afford it, and decide it's the best fit for
you after researching it, then what other people think should be irrelevant. You will always be able to find someone on an internet forum who thinks your choice is the stupidest thing they ever heard of.
Sometimes they're right, and sometimes they're wrong. But in the end, it's your rifle. As long as you made an informed decision after considering your needs and budget, and the actual capabilities and reputation of the product, then you did good.
Of course, if you don't really know what you need, don't properly research your purchase and buy blindly, then yeah, you probably screwed up.