Hello there,
The Starcaster neck is made of lower quality maple than the Fender MIM necks. Also there is a lot of difference in the quality of the construction. I have used several Starcaster necks on projects. Here is what I found with all of them.
Frets. The edges of the frets are quite sharp. You will need to file them down to make the edges smooth and more comfortable to play. I had one Starcaster neck that the fret ends were so sharp they could cut your fingers.
Finish. The maple fretboard on the Starcaster neck is unfinished. There is no lacquer or polyurethane on it at all. If you play on the neck as it is, it gets dirty looking and discolored fast. Fast as in a few hours of playing, not a few months. The finish on the headstock is a semigloss and not very attractive. I have had to refinish every Starcaster neck that I used.
Proflie. The Starcaster necks have a thick C, or clunky as some call it, profile. They because of that they are a little heavier. I used them when I needed a heavier neck to balance the guitar better than a thinner MIM neck. If you like a thick neck, they are fine. If you want a thinner profile, you will not like the feel of a Starcaster neck. They are definitely a thick profile (curvature of the back side of the neck).
Cost. Maple Starcaster necks with the 70s large headstock sell for around $39 on eBay. The pointy Starcaster necks sell for much less, but who wants that headstock shape? You will spend maybe an hour working down the frets and dressing them. Then you will spend a few hours refinishing the neck. Depends on how much you value your time in determining that cost. A used MIM Fender Standard neck will sell for around $115 on eBay. Sure some go higher, but I have also bought them for $85. The MIM Fender neck is a lot better made. So there is not as much difference in the price as you suggest, not after you consider the cost of getting the Starcaster neck worked up to playing shape.
Also, you can get a Mighty Mite neck for $90 off eBay. I see used ones sell for as little as $65. Those are licensed by Fender and made to Fender specs. They come in different profiles, radius and headstock shapes. I have used a few MM necks and found them to be very good necks for the money. I have not had to rework a MM neck to get it in shape to play. The factory does a good job with those.
Some of the Squier necks come with a maple fretboard and those necks are better than the Starcaster neck. They also come in a thinner profile and are already finished. $50 should buy you a used Squier neck with a maple fretboard, unless it is from a Squier Standard. The Standards are very good guitars and the necks bring more, $75 to $90.
Later,