WARNING: Long post ahead.
She-Ra is currently set at ~$350. For a premium to even maybe, kinda, from a place of love kinda way, make sense for Mer-Man it would have to be at least $450 - $500 AFTER DISCOUNT.
Maybe, maybe if he took blind faith POs (no prototype) just showed concept art and he got 100 orders at $500 a piece in the first 3 days it would have enought momentum to be worth it.
The She-Ra EX isn't totally sold out even at 250 due to cancels. 250 @ $350 = $87,500. Let's assume She-Ra sells out and PCS gets that.
Now according to Jerry She-Ra was the most requested character after He-Man. What that means is Mer-Man isn't doing 250 in sales. For the same income PCS would have to sell 175 @ $500 each. Selling that many Mer-Mans may be possible but at that price may not be. Plus he's selling in a character in a known dying line with little to no future.
Now production costs. Jerry has said the factories don't reallly want to do anything less than 200 pieces as it isn't worth it. I kinda doubt the factories care to charge by a percentage of PCS's sales price. They likely charge per piece and that affects their income. A smaller ES likely equates to higher production costs. How much I have no clue.
Could production costs for 175 at a higher price be the same as 250 at a lower price again I don't know but whatever that cost is it would come out of that $87,500. Let's say production cost is half that income so $43,750 left. Now take out a lower conservative of $23,750 for an estimate of design costs and you've got $20,000 of profit.
Or Jerry can use those same resources (not just design and production but customer service, website design, etc. ) and do another Street Fighter piece at ~$390 (an guestimate at an average selling price for Oni considering all discount options) and sell at least 500 for $195,500 income. Take out half for production (which has an even better chance of being a lessser percentage since you're making so many) and you have $97,500 left. Now since it's SF let's take out $37,500 for the proto design and you have $60,000 in income.
That's 3 TIMES the PROFIT for PCS for roughly the same amount of work from PCS.
SF and MK get the benefit of Jerry sculpting SOMETHING for them like the 1/3s or the big beasts. MOTU is just management and direction from Jerry's perspective.
In other word's Jerry sculpting something is less money PCS has to pay out to hire another sculptors work. Plus he doesn't get the satisfaction of sculpting something he himself wants to do and he's already done a large stable of MOTU big guns so maybe there's less for Jerry to see as an achievement.
Plus $20,000 won't even pay an employees salary and PCS now has 3 customer service reps instead of 1 like they had 2-3 years ago. I'm not blaming CS just an easily known increase in expense for PCS.
This is just an analysis with a LOT of guesswork with what tiny bit I "know". This isn't even counting Reg sales. It's easy to discount them as not important as "icing on the cake" but "icing" can be great and they do make some money on them and I'm sure other countries' retailers have much better sales of SF/MK than MOTU. Plus PCS is competing in an industry where a 1000 ES is easily the norm.
And this is from someone that really wants Mer-Man!