I guess that's an "affordable" way to complete your mercury dime collection! I for one, do like a coin with a little bit of "experience" on it. However many mercury dimes can be bought in MS/AU shape for a fair price tag. I'm not totally sure how great this would look next to MS coins, but hey collect how you wish. $295
$390, and the winner will think he got a bargain because it didn't go over $400. Good luck getting a "problem-free" PCGS AG03 for any less. Lowball collectors can find examples much worse.
Anybody guessing less than $300 (including you OP) is tweaking. You won’t find 1916-D cheaper than $200 and this is at the very low end of the spectrum taking details graded coins into account. With that said, I will guess $425. It is on the low end of the AG3 spectrum, considering that half the mint mark is worn away. A solid AG should have a full mint mark, this is right on the edge of being Fair. Eye appeal is also below average with that surface color. But regardless, it is a 1916-D. 6 or 7 years ago I would’ve died for even that one.
This is just like watching The Price Is Right on TV. "What's the highest bid, Drew? I'll go a dollar more." As for myself, I'd rather look at Rachel... MS66, looks like.