@Jilly92 I'd stay away from it personally that's just my opinion...
Offer the guy 10 - 20$ since it's not a bi color and its brown, the polyps look kinda funky as stated above, it could be alk swing could be a new tank, improper placement or overall just an unhealthy coral... idk ... It may have been ticked at the time of the photo shoot or eating it's hard to tell without a closer picture of the skeleton to see if there are any tears, inspect the piece for jelly,nucisene algae on skelton,any pokes or tears in the flesh,gunk around tissue or polyps are a no go for me,look for pests like pygmatrid snails,vermitid snails, barnacles, rock boring clams,
Rember to dip it and keep it away from any coral if u do decide to buy it for atleast a week or two,especially if you have other euphillidae,hammers torches yayas divisa( foxes and bubbles by technicality)
Also take caution when handling euphillidae barehanded, as yayamensis seem to be the euphillidae in which ,certain people get stung by and are the most allergic to and reactive too out of the euphillya family. these guys also have long swepper tentacles that can reach up to triple the length of the coral ;at night for this reason they shouldnt be placed in close proximity to other corals, contrary to what people believe even other euphillidae of the same phylum and order can sting and make each other;retract or even in severe cases eject polyps which will eventually lead to a decline In coral health or even the demise of the coral, i hope this helps you out @Jilly92
@Jilly92 ive bought some cheap green frogspawn frags from https://shop.terrareef.com/products/green-frogspawn-coral
And they ended up florescening blue tips 51$ is a steal for two heads of green frogspawn(100$ at my lfs for a small head non bicolor green and black)
Hammers are pretty neat too you can find that often time that these offer the same movement as the frogspawn and octospawn but are less aggressive when it comes to stinging other eupiliya as long as they are placed by the same species,and are half the price you can find hammer frags from 15$ online aquacultured compared to the 50 to 75$ a head the lfs charges https://www.thefraglab.com/product-page/toxic-green-hammer