left field economy
If you are strictly talking economics, you should not put more money into your boat than what you expect to get for her when you sell her. If that limits your spending, there is another way to 'overspend' yet not give away your upgrades. Ensure that as much as possible, the upgrades you purchase are portable for boat to boat. I have a roller furler that I have move with me from four boats ago; a portable VHF from two boats ago, a PFD from three boats ago, a multiband radio from who know when, a DRS from two boats ago... get the picture... I stripped previous boats down to sellable minimums prior to selling. Many buyers want a low price anyhow, so you can strip down, keep your portable gear, move it to the next boat, and get a value added bonus to build on.In an economic sense, if you bought a boat for $7500, added $4000 worth of gear to her, but suspect that at sale time you will only get $10,000 for her, you need to strip off (7.5k+4k-10k=)$1500 worth of gear to recoup your potential loss.Put a value of pleasure into the formula however, and the boat becomes priceless. Similarily, if you add the value of your labor to the boat, you quickly outprice yourself, as others have stated.