They can explain, cheerfully, that its too expensive - except perhaps as a birthday or holiday gift - or that the child will have to contribute to its purchase from an allowance or from the earnings of an outside job.
1.except 是介词，意思是“除去”；perhaps 是副词，意思是“大约”；as 是介词表示“作为”。是如此吗?
2. as a birthday or holiday gift 这个短语的的意思是?
句子非常简单，不要考虑复杂。为了更好理解句子结构，大家借助 “奥卡姆剃刀原理” 删繁就简，把非必须的繁枝末节剔除：
They can explain that its too expensive except perhaps as a birthday or holiday gift.
【翻译】他们可能讲解说：这东西太贵了，或许作为过生日礼物或节日礼物时除外。
（注意：英汉颜色对应）
1. 介词except 表示“例外状况”，指too expensive 时的例外状况，就是说，某产品作为“过生日礼物或节日礼物”时，就不算“太贵了”。
2. as a birthday or holiday gift：as 表示“身份”或“时间”，都可以讲解通：作为过生日礼物或节日礼物时。
3. perhaps 是“推断副词”，跟maybe 意思基本相同。通常放在被它修饰的词汇之前，本句修饰as a birthday or holiday gift：或许在作为过生日礼物或节日礼物时。
