Frankly the seller has offered various ways to resolve the situation and the BUYER decided that sending the extra $75 was what HE wanted to do.
Since the buyer agreed to pay the extra $75 and take the red tegu and the B&W tegu, then he should live up to it. He said he would send the money on friday. Whether he works, or he doesn't have the money is irrelevant. He said "This is the deal I want" and he should have to live up to it.
"The customer is always right" is a good way to just throw away your product AND your money. GOod customer service is wonderful, but getting screwed out of what the BUYER decided to pay is NOT showing good customer service, it's getting screwed out of your money.
If this was a simpler deal and the seller had shipped JUST the tegu out for $75, with the buyer supposed to send the $75 on friday, would you STILL say "Oh you should just eat the $75, the customer is always right" and say that because the buyer doesn't have the promised payment that he should have however long to pay it, or even not have to pay it at all?
The original deal fell through when one B&W tegu was lost, the seller offered SEVERAL alternative deals, INCLUDING negating the entire deal and shipping the snakes back. The buyer decided on one of the new deals, and promised payment on a specific day, and then never sent the money. The seller is due that money.
Any way you cut it, the buyer owed $75 on friday and has not paid, and has instead decided to say "I'll pay you when I get the money" even though several OTHER options have been offered up, including negating the entire deal and having his snakes returned.
Personally, I think the seller has been more than fair, although it's only been a few days, how long do you go past the "due by" date before it's okay to not have your money? My electric company doesn't let me have electric if I don't pay, why should the seller have to sit and wait for his money until the buyer feels like paying him?