GWS makes the pico servos, they are just about the same as the hs-55's but weigh slightly less and are about 3-5 bucks cheaper.

If you check on ebay theirs constantly Buy it nows on these little yellow 9 gram servos (I think hs-55s are 7 grams). Ive never tried them but they are pretty cheap. I think they are like 9 dollars plus 6 or so for shipping, but I beleive you can get as many as you want for one shipping price so in the end you come out a lot cheaper.

Another item you might be interested in on ebay is these little blue 5 gram servos, they are buy it now for $1 but the shipping is $14 (thats why they sell them for $1 LOL) plus like $12 for each extra servo.

Heres some ebay links if your interested.

[link=http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=2563&item=59258910 81&rd=1]5 gram $1 servos[/link]

[link=http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=2563&item=59242770 73&rd=1]10 gram servo, $8[/link]

[link=http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=2563&item=59253152 01&rd=1]9 gram servo, $9 good deal[/link] you can get 4 of these for 42 bucks (that includes shipping!)

[link=http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=2563&item=59246092 03&rd=1]another $9 9 gram servo[/link] Thse look cheaply made to me but they are cheap and shipping is very cheap as well (for 4 your looking at about $45)

I have hs-55s and they are very good, have had many wrecks using them and they still work great no stripped gears or anything. The only problem ive had is a screw fell out of one, but they come with extras so its no big deal.

Just keep this in mind, "the good stuff aint cheap, and the cheap stuff aint good" you get what you pay for so I wouldnt expect too much out the cheapies on ebay.

EDIT, just noticed none of my links work. I checked and everythign is correct but I guess this site doenst allow you to post a link to ebay as the link has "ebay" starred out therefore when you click it it wont work.