Who is telling you that you need to replace the chain, cassette, CRANKS(?), etc. at 3,000 miles. This is ridiculous. Why have you already replaced the chain so frequently? A dirty chain or cassette attracts dirt and wears faster, but two times already?

Each flat costs you $5? Um, have you tried patching the tubes? Wood screws could decimate most tires so flats after that are not surprising. If we are motivated, we change the tube on the road and patch the old tube in the comforts of home.