'Skip a lunch or two out'. Eating out is expensive. If you avoid eating out once or twice you will save some money. The IEM is $55, the price of a few meals out. Therefore, if you avoid eating out a couple of times, you will be able to afford this IEM.
'Put this in your arsenal' is not to be taken literally, amir is referring to your collection of audio gear as your 'arsenal'. Do not worry, he is not suggesting you can use this IEM as an offensive weapon.
'even if you are not a regular IEM user'. His praise is high enough that he considers it worthwhile buying, for example by setting aside money that would otherwise be used to buy lunches out, even if you do not use IEMs regularly. In other words, for the times that you
do use IEMs, he would recommend these be the ones.
Loving the quality discourse some bring to ASR as usual.