Yeah, that's what I thought. Spending your money on fertilizer would give you more stats in the end than a weapon would... I think Jon should multiply the bonus on weapons by 10 , then they would be worth while.
I always thought it would be cool if the weapons just added a % instead of a set number, that way they would always be useful and certain weapons would be better for you depending on your build.
Nothing crazy, maybe have the cheaper weapons add a set number, for new players, and then the more expensive weapons could add(or even subtract) percentages.