Uhmmm.... Those little trees won´t even reach the pre-bonsai status. Inexistent taper, long leggy branches, sparse foliage... If you do buy them, please, be prepared for spending a lot of time and efforts on them.
That said, if your aim is to practice your bonsai abilities with say "lesser trees" and you don´t expect having a great specimen and provided the asked price is actually to give them away, then I´d say go for it. I started myself this hobby with an ugly fat rooted Ginseng Ficus that at the moment was given away to me.
Learning always comes step by step and generally as an iterative process. Also, looking for the Pistacea Lentiscus surely would help. This link is in Spanish, sorry for that, but it might help your cause.
nintaibonsai.wordpress.com/pistacho/
Alain
